diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/.gitattributes b/serverside_challenge_1/challenges/MasafumiKondo07/.gitattributes
new file mode 100644
index 000000000..31eeee0b6
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/.gitattributes
@@ -0,0 +1,7 @@
+# See https://git-scm.com/docs/gitattributes for more about git attribute files.
+
+# Mark the database schema as having been generated.
+db/schema.rb linguist-generated
+
+# Mark any vendored files as having been vendored.
+vendor/* linguist-vendored
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/.gitignore b/serverside_challenge_1/challenges/MasafumiKondo07/.gitignore
new file mode 100644
index 000000000..e16dc71d2
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/.gitignore
@@ -0,0 +1,31 @@
+# See https://help.github.com/articles/ignoring-files for more about ignoring files.
+#
+# If you find yourself ignoring temporary files generated by your text editor
+# or operating system, you probably want to add a global ignore instead:
+#   git config --global core.excludesfile '~/.gitignore_global'
+
+# Ignore bundler config.
+/.bundle
+
+# Ignore all logfiles and tempfiles.
+/log/*
+/tmp/*
+!/log/.keep
+!/tmp/.keep
+
+# Ignore pidfiles, but keep the directory.
+/tmp/pids/*
+!/tmp/pids/
+!/tmp/pids/.keep
+
+# Ignore uploaded files in development.
+/storage/*
+!/storage/.keep
+/tmp/storage/*
+!/tmp/storage/
+!/tmp/storage/.keep
+
+/public/assets
+
+# Ignore master key for decrypting credentials and more.
+/config/master.key
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/.rspec b/serverside_challenge_1/challenges/MasafumiKondo07/.rspec
new file mode 100644
index 000000000..c99d2e739
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/.rspec
@@ -0,0 +1 @@
+--require spec_helper
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/.ruby-version b/serverside_challenge_1/challenges/MasafumiKondo07/.ruby-version
new file mode 100644
index 000000000..7bde84d06
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/.ruby-version
@@ -0,0 +1 @@
+ruby-3.1.2
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/Dockerfile b/serverside_challenge_1/challenges/MasafumiKondo07/Dockerfile
new file mode 100644
index 000000000..f1e7066bb
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/Dockerfile
@@ -0,0 +1,17 @@
+FROM ruby:3.1
+
+RUN mkdir /myapp
+WORKDIR /myapp
+COPY Gemfile /myapp/Gemfile
+COPY Gemfile.lock /myapp/Gemfile.lock
+RUN bundle install
+COPY . /myapp
+
+# Add a script to be executed every time the container starts.
+COPY entrypoint.sh /usr/bin/
+RUN chmod +x /usr/bin/entrypoint.sh
+ENTRYPOINT ["entrypoint.sh"]
+EXPOSE 3000
+
+# Start the main process.
+CMD ["rails", "server", "-b", "0.0.0.0"]
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/Gemfile b/serverside_challenge_1/challenges/MasafumiKondo07/Gemfile
new file mode 100644
index 000000000..2daf3a0d4
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/Gemfile
@@ -0,0 +1,74 @@
+source "https://rubygems.org"
+git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
+ruby "3.1.2"
+
+# Bundle edge Rails instead: gem "rails", github: "rails/rails", branch: "main"
+gem "rails", "~> 7.0.4"
+
+# The original asset pipeline for Rails [https://github.com/rails/sprockets-rails]
+gem "sprockets-rails"
+
+# Use mysql as the database for Active Record
+gem "mysql2", "~> 0.5"
+
+# Use the Puma web server [https://github.com/puma/puma]
+gem "puma", "~> 5.0"
+
+# Use JavaScript with ESM import maps [https://github.com/rails/importmap-rails]
+gem "importmap-rails"
+
+# Hotwire's SPA-like page accelerator [https://turbo.hotwired.dev]
+gem "turbo-rails"
+
+# Hotwire's modest JavaScript framework [https://stimulus.hotwired.dev]
+gem "stimulus-rails"
+
+# Build JSON APIs with ease [https://github.com/rails/jbuilder]
+gem "jbuilder"
+
+# Use Redis adapter to run Action Cable in production
+# gem "redis", "~> 4.0"
+
+# Use Kredis to get higher-level data types in Redis [https://github.com/rails/kredis]
+# gem "kredis"
+
+# Use Active Model has_secure_password [https://guides.rubyonrails.org/active_model_basics.html#securepassword]
+# gem "bcrypt", "~> 3.1.7"
+
+# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
+gem "tzinfo-data", platforms: %i[ mingw mswin x64_mingw jruby ]
+
+# Reduces boot times through caching; required in config/boot.rb
+gem "bootsnap", require: false
+
+# Use Sass to process CSS
+# gem "sassc-rails"
+
+# Use Active Storage variants [https://guides.rubyonrails.org/active_storage_overview.html#transforming-images]
+# gem "image_processing", "~> 1.2"
+
+group :development, :test do
+  # See https://guides.rubyonrails.org/debugging_rails_applications.html#debugging-with-the-debug-gem
+  gem "debug", platforms: %i[ mri mingw x64_mingw ]
+  gem 'factory_bot_rails'
+end
+
+group :development do
+  # Use console on exceptions pages [https://github.com/rails/web-console]
+  gem "web-console"
+  gem 'rspec-rails'
+
+  # Add speed badges [https://github.com/MiniProfiler/rack-mini-profiler]
+  # gem "rack-mini-profiler"
+
+  # Speed up commands on slow machines / big apps [https://github.com/rails/spring]
+  # gem "spring"
+end
+
+group :test do
+  # Use system testing [https://guides.rubyonrails.org/testing.html#system-testing]
+  gem "capybara"
+  gem "selenium-webdriver"
+  gem "webdrivers"
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/Gemfile.lock b/serverside_challenge_1/challenges/MasafumiKondo07/Gemfile.lock
new file mode 100644
index 000000000..00d5de332
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/Gemfile.lock
@@ -0,0 +1,262 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    actioncable (7.0.4)
+      actionpack (= 7.0.4)
+      activesupport (= 7.0.4)
+      nio4r (~> 2.0)
+      websocket-driver (>= 0.6.1)
+    actionmailbox (7.0.4)
+      actionpack (= 7.0.4)
+      activejob (= 7.0.4)
+      activerecord (= 7.0.4)
+      activestorage (= 7.0.4)
+      activesupport (= 7.0.4)
+      mail (>= 2.7.1)
+      net-imap
+      net-pop
+      net-smtp
+    actionmailer (7.0.4)
+      actionpack (= 7.0.4)
+      actionview (= 7.0.4)
+      activejob (= 7.0.4)
+      activesupport (= 7.0.4)
+      mail (~> 2.5, >= 2.5.4)
+      net-imap
+      net-pop
+      net-smtp
+      rails-dom-testing (~> 2.0)
+    actionpack (7.0.4)
+      actionview (= 7.0.4)
+      activesupport (= 7.0.4)
+      rack (~> 2.0, >= 2.2.0)
+      rack-test (>= 0.6.3)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.2.0)
+    actiontext (7.0.4)
+      actionpack (= 7.0.4)
+      activerecord (= 7.0.4)
+      activestorage (= 7.0.4)
+      activesupport (= 7.0.4)
+      globalid (>= 0.6.0)
+      nokogiri (>= 1.8.5)
+    actionview (7.0.4)
+      activesupport (= 7.0.4)
+      builder (~> 3.1)
+      erubi (~> 1.4)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.1, >= 1.2.0)
+    activejob (7.0.4)
+      activesupport (= 7.0.4)
+      globalid (>= 0.3.6)
+    activemodel (7.0.4)
+      activesupport (= 7.0.4)
+    activerecord (7.0.4)
+      activemodel (= 7.0.4)
+      activesupport (= 7.0.4)
+    activestorage (7.0.4)
+      actionpack (= 7.0.4)
+      activejob (= 7.0.4)
+      activerecord (= 7.0.4)
+      activesupport (= 7.0.4)
+      marcel (~> 1.0)
+      mini_mime (>= 1.1.0)
+    activesupport (7.0.4)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
+    addressable (2.8.1)
+      public_suffix (>= 2.0.2, < 6.0)
+    bindex (0.8.1)
+    bootsnap (1.13.0)
+      msgpack (~> 1.2)
+    builder (3.2.4)
+    capybara (3.37.1)
+      addressable
+      matrix
+      mini_mime (>= 0.1.3)
+      nokogiri (~> 1.8)
+      rack (>= 1.6.0)
+      rack-test (>= 0.6.3)
+      regexp_parser (>= 1.5, < 3.0)
+      xpath (~> 3.2)
+    childprocess (4.1.0)
+    concurrent-ruby (1.1.10)
+    crass (1.0.6)
+    debug (1.6.2)
+      irb (>= 1.3.6)
+      reline (>= 0.3.1)
+    diff-lcs (1.5.0)
+    digest (3.1.0)
+    erubi (1.11.0)
+    factory_bot (6.2.1)
+      activesupport (>= 5.0.0)
+    factory_bot_rails (6.2.0)
+      factory_bot (~> 6.2.0)
+      railties (>= 5.0.0)
+    globalid (1.0.0)
+      activesupport (>= 5.0)
+    i18n (1.12.0)
+      concurrent-ruby (~> 1.0)
+    importmap-rails (1.1.5)
+      actionpack (>= 6.0.0)
+      railties (>= 6.0.0)
+    io-console (0.5.11)
+    irb (1.4.1)
+      reline (>= 0.3.0)
+    jbuilder (2.11.5)
+      actionview (>= 5.0.0)
+      activesupport (>= 5.0.0)
+    loofah (2.18.0)
+      crass (~> 1.0.2)
+      nokogiri (>= 1.5.9)
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    marcel (1.0.2)
+    matrix (0.4.2)
+    method_source (1.0.0)
+    mini_mime (1.1.2)
+    minitest (5.16.3)
+    msgpack (1.5.6)
+    mysql2 (0.5.4)
+    net-imap (0.2.3)
+      digest
+      net-protocol
+      strscan
+    net-pop (0.1.1)
+      digest
+      net-protocol
+      timeout
+    net-protocol (0.1.3)
+      timeout
+    net-smtp (0.3.1)
+      digest
+      net-protocol
+      timeout
+    nio4r (2.5.8)
+    nokogiri (1.13.8-x86_64-linux)
+      racc (~> 1.4)
+    public_suffix (5.0.0)
+    puma (5.6.5)
+      nio4r (~> 2.0)
+    racc (1.6.0)
+    rack (2.2.4)
+    rack-test (2.0.2)
+      rack (>= 1.3)
+    rails (7.0.4)
+      actioncable (= 7.0.4)
+      actionmailbox (= 7.0.4)
+      actionmailer (= 7.0.4)
+      actionpack (= 7.0.4)
+      actiontext (= 7.0.4)
+      actionview (= 7.0.4)
+      activejob (= 7.0.4)
+      activemodel (= 7.0.4)
+      activerecord (= 7.0.4)
+      activestorage (= 7.0.4)
+      activesupport (= 7.0.4)
+      bundler (>= 1.15.0)
+      railties (= 7.0.4)
+    rails-dom-testing (2.0.3)
+      activesupport (>= 4.2.0)
+      nokogiri (>= 1.6)
+    rails-html-sanitizer (1.4.3)
+      loofah (~> 2.3)
+    railties (7.0.4)
+      actionpack (= 7.0.4)
+      activesupport (= 7.0.4)
+      method_source
+      rake (>= 12.2)
+      thor (~> 1.0)
+      zeitwerk (~> 2.5)
+    rake (13.0.6)
+    regexp_parser (2.5.0)
+    reline (0.3.1)
+      io-console (~> 0.5)
+    rexml (3.2.5)
+    rspec-core (3.11.0)
+      rspec-support (~> 3.11.0)
+    rspec-expectations (3.11.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-mocks (3.11.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-rails (5.1.2)
+      actionpack (>= 5.2)
+      activesupport (>= 5.2)
+      railties (>= 5.2)
+      rspec-core (~> 3.10)
+      rspec-expectations (~> 3.10)
+      rspec-mocks (~> 3.10)
+      rspec-support (~> 3.10)
+    rspec-support (3.11.1)
+    rubyzip (2.3.2)
+    selenium-webdriver (4.4.0)
+      childprocess (>= 0.5, < 5.0)
+      rexml (~> 3.2, >= 3.2.5)
+      rubyzip (>= 1.2.2, < 3.0)
+      websocket (~> 1.0)
+    sprockets (4.1.1)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (3.4.2)
+      actionpack (>= 5.2)
+      activesupport (>= 5.2)
+      sprockets (>= 3.0.0)
+    stimulus-rails (1.1.0)
+      railties (>= 6.0.0)
+    strscan (3.0.4)
+    thor (1.2.1)
+    timeout (0.3.0)
+    turbo-rails (1.1.1)
+      actionpack (>= 6.0.0)
+      activejob (>= 6.0.0)
+      railties (>= 6.0.0)
+    tzinfo (2.0.5)
+      concurrent-ruby (~> 1.0)
+    web-console (4.2.0)
+      actionview (>= 6.0.0)
+      activemodel (>= 6.0.0)
+      bindex (>= 0.4.0)
+      railties (>= 6.0.0)
+    webdrivers (5.0.0)
+      nokogiri (~> 1.6)
+      rubyzip (>= 1.3.0)
+      selenium-webdriver (~> 4.0)
+    websocket (1.2.9)
+    websocket-driver (0.7.5)
+      websocket-extensions (>= 0.1.0)
+    websocket-extensions (0.1.5)
+    xpath (3.2.0)
+      nokogiri (~> 1.8)
+    zeitwerk (2.6.0)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  bootsnap
+  capybara
+  debug
+  factory_bot_rails
+  importmap-rails
+  jbuilder
+  mysql2 (~> 0.5)
+  puma (~> 5.0)
+  rails (~> 7.0.4)
+  rspec-rails
+  selenium-webdriver
+  sprockets-rails
+  stimulus-rails
+  turbo-rails
+  tzinfo-data
+  web-console
+  webdrivers
+
+RUBY VERSION
+   ruby 3.1.2p20
+
+BUNDLED WITH
+   2.3.7
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/README.md b/serverside_challenge_1/challenges/MasafumiKondo07/README.md
new file mode 100644
index 000000000..7db80e4ca
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/README.md
@@ -0,0 +1,24 @@
+# README
+
+This README would normally document whatever steps are necessary to get the
+application up and running.
+
+Things you may want to cover:
+
+* Ruby version
+
+* System dependencies
+
+* Configuration
+
+* Database creation
+
+* Database initialization
+
+* How to run the test suite
+
+* Services (job queues, cache servers, search engines, etc.)
+
+* Deployment instructions
+
+* ...
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/Rakefile b/serverside_challenge_1/challenges/MasafumiKondo07/Rakefile
new file mode 100644
index 000000000..9a5ea7383
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/Rakefile
@@ -0,0 +1,6 @@
+# Add your own tasks in files placed in lib/tasks ending in .rake,
+# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
+
+require_relative "config/application"
+
+Rails.application.load_tasks
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/config/manifest.js b/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/config/manifest.js
new file mode 100644
index 000000000..ddd546a0b
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/config/manifest.js
@@ -0,0 +1,4 @@
+//= link_tree ../images
+//= link_directory ../stylesheets .css
+//= link_tree ../../javascript .js
+//= link_tree ../../../vendor/javascript .js
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/images/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/images/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/stylesheets/application.css b/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/stylesheets/application.css
new file mode 100644
index 000000000..288b9ab71
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/assets/stylesheets/application.css
@@ -0,0 +1,15 @@
+/*
+ * This is a manifest file that'll be compiled into application.css, which will include all the files
+ * listed below.
+ *
+ * Any CSS (and SCSS, if configured) file within this directory, lib/assets/stylesheets, or any plugin's
+ * vendor/assets/stylesheets directory can be referenced here using a relative path.
+ *
+ * You're free to add application-wide styles to this file and they'll appear at the bottom of the
+ * compiled file so the styles you add here take precedence over styles defined in any other CSS
+ * files in this directory. Styles in this file should be added after the last require_* statement.
+ * It is generally better to create a new file per style scope.
+ *
+ *= require_tree .
+ *= require_self
+ */
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/channels/application_cable/channel.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/channels/application_cable/channel.rb
new file mode 100644
index 000000000..d67269728
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/channels/application_cable/channel.rb
@@ -0,0 +1,4 @@
+module ApplicationCable
+  class Channel < ActionCable::Channel::Base
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/channels/application_cable/connection.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/channels/application_cable/connection.rb
new file mode 100644
index 000000000..0ff5442f4
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/channels/application_cable/connection.rb
@@ -0,0 +1,4 @@
+module ApplicationCable
+  class Connection < ActionCable::Connection::Base
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/api/v1/electricity_charges_simulators_controller.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/api/v1/electricity_charges_simulators_controller.rb
new file mode 100644
index 000000000..f1a0c5d55
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/api/v1/electricity_charges_simulators_controller.rb
@@ -0,0 +1,33 @@
+module Api
+  module V1
+    class ElectricityChargesSimulatorsController < ApplicationController
+      def index
+        simulation_list = []
+        Company.preload(:plans).all.each do |company|
+          company.plans.each do |plan|
+            basic_charge_instance = plan.basic_charges.find_by(ampere: params[:ampere])
+            next if basic_charge_instance.nil?
+
+            # 従量料金の計算
+            total_electricity_fee = ElectricityFee.calc(plan, params[:amount_used].to_i)
+            
+            simulation_list << {company_name: company.name, plan_name: plan.name, price: plan.applicable_plan_fee(basic_charge_instance.price, total_electricity_fee)}
+          end
+        end
+        # 指定された基本料金でのプランが見つからない場合、エラーメッセージを返却
+        if (simulation_list.blank?)
+          render json: error_object
+          return
+        end
+        render json: simulation_list
+      end
+
+      private
+      def error_object
+        {
+          message: "指定されたアンペア数での料金プランは見つかりませんでした。"
+        }
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/application_controller.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/application_controller.rb
new file mode 100644
index 000000000..09705d12a
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/application_controller.rb
@@ -0,0 +1,2 @@
+class ApplicationController < ActionController::Base
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/concerns/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/app/controllers/concerns/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/helpers/application_helper.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/helpers/application_helper.rb
new file mode 100644
index 000000000..de6be7945
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/helpers/application_helper.rb
@@ -0,0 +1,2 @@
+module ApplicationHelper
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/application.js b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/application.js
new file mode 100644
index 000000000..0d7b49404
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/application.js
@@ -0,0 +1,3 @@
+// Configure your import map in config/importmap.rb. Read more: https://github.com/rails/importmap-rails
+import "@hotwired/turbo-rails"
+import "controllers"
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/application.js b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/application.js
new file mode 100644
index 000000000..1213e85c7
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/application.js
@@ -0,0 +1,9 @@
+import { Application } from "@hotwired/stimulus"
+
+const application = Application.start()
+
+// Configure Stimulus development experience
+application.debug = false
+window.Stimulus   = application
+
+export { application }
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/hello_controller.js b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/hello_controller.js
new file mode 100644
index 000000000..5975c0789
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/hello_controller.js
@@ -0,0 +1,7 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  connect() {
+    this.element.textContent = "Hello World!"
+  }
+}
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/index.js b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/index.js
new file mode 100644
index 000000000..54ad4cad4
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/javascript/controllers/index.js
@@ -0,0 +1,11 @@
+// Import and register all your controllers from the importmap under controllers/*
+
+import { application } from "controllers/application"
+
+// Eager load all controllers defined in the import map under controllers/**/*_controller
+import { eagerLoadControllersFrom } from "@hotwired/stimulus-loading"
+eagerLoadControllersFrom("controllers", application)
+
+// Lazy load controllers as they appear in the DOM (remember not to preload controllers in import map!)
+// import { lazyLoadControllersFrom } from "@hotwired/stimulus-loading"
+// lazyLoadControllersFrom("controllers", application)
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/jobs/application_job.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/jobs/application_job.rb
new file mode 100644
index 000000000..d394c3d10
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/jobs/application_job.rb
@@ -0,0 +1,7 @@
+class ApplicationJob < ActiveJob::Base
+  # Automatically retry jobs that encountered a deadlock
+  # retry_on ActiveRecord::Deadlocked
+
+  # Most jobs are safe to ignore if the underlying records are no longer available
+  # discard_on ActiveJob::DeserializationError
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/mailers/application_mailer.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/mailers/application_mailer.rb
new file mode 100644
index 000000000..3c34c8148
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/mailers/application_mailer.rb
@@ -0,0 +1,4 @@
+class ApplicationMailer < ActionMailer::Base
+  default from: "from@example.com"
+  layout "mailer"
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/models/application_record.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/application_record.rb
new file mode 100644
index 000000000..b63caeb8a
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/application_record.rb
@@ -0,0 +1,3 @@
+class ApplicationRecord < ActiveRecord::Base
+  primary_abstract_class
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/models/basic_charge.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/basic_charge.rb
new file mode 100644
index 000000000..5799bfc9c
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/basic_charge.rb
@@ -0,0 +1,3 @@
+class BasicCharge < ApplicationRecord
+  belongs_to :plan
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/models/company.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/company.rb
new file mode 100644
index 000000000..32d2c20eb
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/company.rb
@@ -0,0 +1,3 @@
+class Company < ApplicationRecord
+  has_many :plans, dependent: :destroy
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/models/concerns/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/concerns/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/models/electricity_fee.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/electricity_fee.rb
new file mode 100644
index 000000000..59bf1e09f
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/electricity_fee.rb
@@ -0,0 +1,14 @@
+class ElectricityFee < ApplicationRecord
+  belongs_to :plan
+  class << self
+    def calc(plan, amount_used)
+      result = 0
+      plan.electricity_fees.where(classification_min: ..amount_used).each do |instance|
+        usage_lower_limit = instance.classification_min == 0 ? 0 : instance.classification_min - 1
+        usage_upper_limit = instance.classification_max.present? && instance.classification_max < amount_used ? instance.classification_max : amount_used
+        result += (usage_upper_limit - usage_lower_limit) * instance.price
+      end
+      result
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/models/plan.rb b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/plan.rb
new file mode 100644
index 000000000..fe5c704c3
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/models/plan.rb
@@ -0,0 +1,9 @@
+class Plan < ApplicationRecord
+  belongs_to :company
+  has_many :electricity_fees, dependent: :destroy
+  has_many :basic_charges, dependent: :destroy
+
+  def applicable_plan_fee(basic_charge, electricity_fee)
+    basic_charge + electricity_fee
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/application.html.erb b/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/application.html.erb
new file mode 100644
index 000000000..06c952212
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/application.html.erb
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Myapp</title>
+    <meta name="viewport" content="width=device-width,initial-scale=1">
+    <%= csrf_meta_tags %>
+    <%= csp_meta_tag %>
+
+    <%= stylesheet_link_tag "application", "data-turbo-track": "reload" %>
+    <%= javascript_importmap_tags %>
+  </head>
+
+  <body>
+    <%= yield %>
+  </body>
+</html>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/mailer.html.erb b/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/mailer.html.erb
new file mode 100644
index 000000000..cbd34d2e9
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/mailer.html.erb
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+    <style>
+      /* Email styles need to be inline */
+    </style>
+  </head>
+
+  <body>
+    <%= yield %>
+  </body>
+</html>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/mailer.text.erb b/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/mailer.text.erb
new file mode 100644
index 000000000..37f0bddbd
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/app/views/layouts/mailer.text.erb
@@ -0,0 +1 @@
+<%= yield %>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/bin/bundle b/serverside_challenge_1/challenges/MasafumiKondo07/bin/bundle
new file mode 100755
index 000000000..5b593cb62
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/bin/bundle
@@ -0,0 +1,114 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'bundle' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "rubygems"
+
+m = Module.new do
+  module_function
+
+  def invoked_as_script?
+    File.expand_path($0) == File.expand_path(__FILE__)
+  end
+
+  def env_var_version
+    ENV["BUNDLER_VERSION"]
+  end
+
+  def cli_arg_version
+    return unless invoked_as_script? # don't want to hijack other binstubs
+    return unless "update".start_with?(ARGV.first || " ") # must be running `bundle update`
+    bundler_version = nil
+    update_index = nil
+    ARGV.each_with_index do |a, i|
+      if update_index && update_index.succ == i && a =~ Gem::Version::ANCHORED_VERSION_PATTERN
+        bundler_version = a
+      end
+      next unless a =~ /\A--bundler(?:[= ](#{Gem::Version::VERSION_PATTERN}))?\z/
+      bundler_version = $1
+      update_index = i
+    end
+    bundler_version
+  end
+
+  def gemfile
+    gemfile = ENV["BUNDLE_GEMFILE"]
+    return gemfile if gemfile && !gemfile.empty?
+
+    File.expand_path("../../Gemfile", __FILE__)
+  end
+
+  def lockfile
+    lockfile =
+      case File.basename(gemfile)
+      when "gems.rb" then gemfile.sub(/\.rb$/, gemfile)
+      else "#{gemfile}.lock"
+      end
+    File.expand_path(lockfile)
+  end
+
+  def lockfile_version
+    return unless File.file?(lockfile)
+    lockfile_contents = File.read(lockfile)
+    return unless lockfile_contents =~ /\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n/
+    Regexp.last_match(1)
+  end
+
+  def bundler_requirement
+    @bundler_requirement ||=
+      env_var_version || cli_arg_version ||
+        bundler_requirement_for(lockfile_version)
+  end
+
+  def bundler_requirement_for(version)
+    return "#{Gem::Requirement.default}.a" unless version
+
+    bundler_gem_version = Gem::Version.new(version)
+
+    requirement = bundler_gem_version.approximate_recommendation
+
+    return requirement unless Gem.rubygems_version < Gem::Version.new("2.7.0")
+
+    requirement += ".a" if bundler_gem_version.prerelease?
+
+    requirement
+  end
+
+  def load_bundler!
+    ENV["BUNDLE_GEMFILE"] ||= gemfile
+
+    activate_bundler
+  end
+
+  def activate_bundler
+    gem_error = activation_error_handling do
+      gem "bundler", bundler_requirement
+    end
+    return if gem_error.nil?
+    require_error = activation_error_handling do
+      require "bundler/version"
+    end
+    return if require_error.nil? && Gem::Requirement.new(bundler_requirement).satisfied_by?(Gem::Version.new(Bundler::VERSION))
+    warn "Activating bundler (#{bundler_requirement}) failed:\n#{gem_error.message}\n\nTo install the version of bundler this project requires, run `gem install bundler -v '#{bundler_requirement}'`"
+    exit 42
+  end
+
+  def activation_error_handling
+    yield
+    nil
+  rescue StandardError, LoadError => e
+    e
+  end
+end
+
+m.load_bundler!
+
+if m.invoked_as_script?
+  load Gem.bin_path("bundler", "bundle")
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/bin/importmap b/serverside_challenge_1/challenges/MasafumiKondo07/bin/importmap
new file mode 100755
index 000000000..36502ab16
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/bin/importmap
@@ -0,0 +1,4 @@
+#!/usr/bin/env ruby
+
+require_relative "../config/application"
+require "importmap/commands"
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/bin/rails b/serverside_challenge_1/challenges/MasafumiKondo07/bin/rails
new file mode 100755
index 000000000..efc037749
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/bin/rails
@@ -0,0 +1,4 @@
+#!/usr/bin/env ruby
+APP_PATH = File.expand_path("../config/application", __dir__)
+require_relative "../config/boot"
+require "rails/commands"
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/bin/rake b/serverside_challenge_1/challenges/MasafumiKondo07/bin/rake
new file mode 100755
index 000000000..4fbf10b96
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/bin/rake
@@ -0,0 +1,4 @@
+#!/usr/bin/env ruby
+require_relative "../config/boot"
+require "rake"
+Rake.application.run
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/bin/setup b/serverside_challenge_1/challenges/MasafumiKondo07/bin/setup
new file mode 100755
index 000000000..ec47b79b3
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/bin/setup
@@ -0,0 +1,33 @@
+#!/usr/bin/env ruby
+require "fileutils"
+
+# path to your application root.
+APP_ROOT = File.expand_path("..", __dir__)
+
+def system!(*args)
+  system(*args) || abort("\n== Command #{args} failed ==")
+end
+
+FileUtils.chdir APP_ROOT do
+  # This script is a way to set up or update your development environment automatically.
+  # This script is idempotent, so that you can run it at any time and get an expectable outcome.
+  # Add necessary setup steps to this file.
+
+  puts "== Installing dependencies =="
+  system! "gem install bundler --conservative"
+  system("bundle check") || system!("bundle install")
+
+  # puts "\n== Copying sample files =="
+  # unless File.exist?("config/database.yml")
+  #   FileUtils.cp "config/database.yml.sample", "config/database.yml"
+  # end
+
+  puts "\n== Preparing database =="
+  system! "bin/rails db:prepare"
+
+  puts "\n== Removing old logs and tempfiles =="
+  system! "bin/rails log:clear tmp:clear"
+
+  puts "\n== Restarting application server =="
+  system! "bin/rails restart"
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config.ru b/serverside_challenge_1/challenges/MasafumiKondo07/config.ru
new file mode 100644
index 000000000..4a3c09a68
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config.ru
@@ -0,0 +1,6 @@
+# This file is used by Rack-based servers to start the application.
+
+require_relative "config/environment"
+
+run Rails.application
+Rails.application.load_server
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/application.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/application.rb
new file mode 100644
index 000000000..243c662ac
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/application.rb
@@ -0,0 +1,22 @@
+require_relative "boot"
+
+require "rails/all"
+
+# Require the gems listed in Gemfile, including any gems
+# you've limited to :test, :development, or :production.
+Bundler.require(*Rails.groups)
+
+module Myapp
+  class Application < Rails::Application
+    # Initialize configuration defaults for originally generated Rails version.
+    config.load_defaults 7.0
+
+    # Configuration for the application, engines, and railties goes here.
+    #
+    # These settings can be overridden in specific environments using the files
+    # in config/environments, which are processed later.
+    #
+    # config.time_zone = "Central Time (US & Canada)"
+    # config.eager_load_paths << Rails.root.join("extras")
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/boot.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/boot.rb
new file mode 100644
index 000000000..988a5ddc4
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/boot.rb
@@ -0,0 +1,4 @@
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../Gemfile", __dir__)
+
+require "bundler/setup" # Set up gems listed in the Gemfile.
+require "bootsnap/setup" # Speed up boot time by caching expensive operations.
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/cable.yml b/serverside_challenge_1/challenges/MasafumiKondo07/config/cable.yml
new file mode 100644
index 000000000..d7187d2e8
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/cable.yml
@@ -0,0 +1,10 @@
+development:
+  adapter: async
+
+test:
+  adapter: test
+
+production:
+  adapter: redis
+  url: <%= ENV.fetch("REDIS_URL") { "redis://localhost:6379/1" } %>
+  channel_prefix: myapp_production
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/credentials.yml.enc b/serverside_challenge_1/challenges/MasafumiKondo07/config/credentials.yml.enc
new file mode 100644
index 000000000..771312a60
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/credentials.yml.enc
@@ -0,0 +1 @@
+eii4CHP9F5KPX3NQODB6ya5MyGViSZHENvCOGQRdz1d68qVP2BviAlp8vNzCWjqAKj6smSx8z4yAMVxDl19kt/DxNQPvtQ8lzZT2Yc3lFdBzt0xzLZGg5zBt6iK6pFxMLX4LJBDxfwkt5Vqv+juD+vBsjHShir3rc7VgGLz19OpE1vR4nFdq5tLYO8Q/ckPFuBaVQEHCyeOZ8i12GwuzUR8py/CM50WP1zyAaH4Py7zDcbUQJ3yCFQfghgwxXx3WTwokC/s9W3ilW25nbXVMyC3VMhJec8uZgQjuhnn+UGEjqsjcI5dSwV7iJVOM+XdB35NgmqAdy/3mQqaYZjBb+47URMCD86g5ApbgkoJyUKnZswkWDBc7WoxQN1Gqd9iS9ClRgowdIBFo2QlmAv7vtK31y5m/1SF0CCNU--7RQ7Q/6hk3e/07UO--GE+Hb8+c+dYlhrMyuy3ifQ==
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/database.yml b/serverside_challenge_1/challenges/MasafumiKondo07/config/database.yml
new file mode 100644
index 000000000..458730df3
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/database.yml
@@ -0,0 +1,55 @@
+# MySQL. Versions 5.5.8 and up are supported.
+#
+# Install the MySQL driver
+#   gem install mysql2
+#
+# Ensure the MySQL gem is defined in your Gemfile
+#   gem "mysql2"
+#
+# And be sure to use new-style password hashing:
+#   https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html
+#
+default: &default
+  adapter: mysql2
+  encoding: utf8mb4
+  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+  username: root
+  password: password
+  host: db
+
+development:
+  <<: *default
+  database: myapp_development
+
+# Warning: The database defined as "test" will be erased and
+# re-generated from your development database when you run "rake".
+# Do not set this db to the same as development or production.
+test:
+  <<: *default
+  database: myapp_test
+
+# As with config/credentials.yml, you never want to store sensitive information,
+# like your database password, in your source code. If your source code is
+# ever seen by anyone, they now have access to your database.
+#
+# Instead, provide the password or a full connection URL as an environment
+# variable when you boot the app. For example:
+#
+#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
+#
+# If the connection URL is provided in the special DATABASE_URL environment
+# variable, Rails will automatically merge its configuration values on top of
+# the values provided in this file. Alternatively, you can specify a connection
+# URL environment variable explicitly:
+#
+#   production:
+#     url: <%= ENV["MY_APP_DATABASE_URL"] %>
+#
+# Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
+# for a full overview on how database connection configuration can be specified.
+#
+production:
+  <<: *default
+  database: myapp_production
+  username: myapp
+  password: <%= ENV["MYAPP_DATABASE_PASSWORD"] %>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/environment.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/environment.rb
new file mode 100644
index 000000000..cac531577
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/environment.rb
@@ -0,0 +1,5 @@
+# Load the Rails application.
+require_relative "application"
+
+# Initialize the Rails application.
+Rails.application.initialize!
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/development.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/development.rb
new file mode 100644
index 000000000..8500f459a
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/development.rb
@@ -0,0 +1,70 @@
+require "active_support/core_ext/integer/time"
+
+Rails.application.configure do
+  # Settings specified here will take precedence over those in config/application.rb.
+
+  # In the development environment your application's code is reloaded any time
+  # it changes. This slows down response time but is perfect for development
+  # since you don't have to restart the web server when you make code changes.
+  config.cache_classes = false
+
+  # Do not eager load code on boot.
+  config.eager_load = false
+
+  # Show full error reports.
+  config.consider_all_requests_local = true
+
+  # Enable server timing
+  config.server_timing = true
+
+  # Enable/disable caching. By default caching is disabled.
+  # Run rails dev:cache to toggle caching.
+  if Rails.root.join("tmp/caching-dev.txt").exist?
+    config.action_controller.perform_caching = true
+    config.action_controller.enable_fragment_cache_logging = true
+
+    config.cache_store = :memory_store
+    config.public_file_server.headers = {
+      "Cache-Control" => "public, max-age=#{2.days.to_i}"
+    }
+  else
+    config.action_controller.perform_caching = false
+
+    config.cache_store = :null_store
+  end
+
+  # Store uploaded files on the local file system (see config/storage.yml for options).
+  config.active_storage.service = :local
+
+  # Don't care if the mailer can't send.
+  config.action_mailer.raise_delivery_errors = false
+
+  config.action_mailer.perform_caching = false
+
+  # Print deprecation notices to the Rails logger.
+  config.active_support.deprecation = :log
+
+  # Raise exceptions for disallowed deprecations.
+  config.active_support.disallowed_deprecation = :raise
+
+  # Tell Active Support which deprecation messages to disallow.
+  config.active_support.disallowed_deprecation_warnings = []
+
+  # Raise an error on page load if there are pending migrations.
+  config.active_record.migration_error = :page_load
+
+  # Highlight code that triggered database queries in logs.
+  config.active_record.verbose_query_logs = true
+
+  # Suppress logger output for asset requests.
+  config.assets.quiet = true
+
+  # Raises error for missing translations.
+  # config.i18n.raise_on_missing_translations = true
+
+  # Annotate rendered view with file names.
+  # config.action_view.annotate_rendered_view_with_filenames = true
+
+  # Uncomment if you wish to allow Action Cable access from any origin.
+  # config.action_cable.disable_request_forgery_protection = true
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/production.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/production.rb
new file mode 100644
index 000000000..a70351bde
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/production.rb
@@ -0,0 +1,93 @@
+require "active_support/core_ext/integer/time"
+
+Rails.application.configure do
+  # Settings specified here will take precedence over those in config/application.rb.
+
+  # Code is not reloaded between requests.
+  config.cache_classes = true
+
+  # Eager load code on boot. This eager loads most of Rails and
+  # your application in memory, allowing both threaded web servers
+  # and those relying on copy on write to perform better.
+  # Rake tasks automatically ignore this option for performance.
+  config.eager_load = true
+
+  # Full error reports are disabled and caching is turned on.
+  config.consider_all_requests_local       = false
+  config.action_controller.perform_caching = true
+
+  # Ensures that a master key has been made available in either ENV["RAILS_MASTER_KEY"]
+  # or in config/master.key. This key is used to decrypt credentials (and other encrypted files).
+  # config.require_master_key = true
+
+  # Disable serving static files from the `/public` folder by default since
+  # Apache or NGINX already handles this.
+  config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
+
+  # Compress CSS using a preprocessor.
+  # config.assets.css_compressor = :sass
+
+  # Do not fallback to assets pipeline if a precompiled asset is missed.
+  config.assets.compile = false
+
+  # Enable serving of images, stylesheets, and JavaScripts from an asset server.
+  # config.asset_host = "http://assets.example.com"
+
+  # Specifies the header that your server uses for sending files.
+  # config.action_dispatch.x_sendfile_header = "X-Sendfile" # for Apache
+  # config.action_dispatch.x_sendfile_header = "X-Accel-Redirect" # for NGINX
+
+  # Store uploaded files on the local file system (see config/storage.yml for options).
+  config.active_storage.service = :local
+
+  # Mount Action Cable outside main process or domain.
+  # config.action_cable.mount_path = nil
+  # config.action_cable.url = "wss://example.com/cable"
+  # config.action_cable.allowed_request_origins = [ "http://example.com", /http:\/\/example.*/ ]
+
+  # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
+  # config.force_ssl = true
+
+  # Include generic and useful information about system operation, but avoid logging too much
+  # information to avoid inadvertent exposure of personally identifiable information (PII).
+  config.log_level = :info
+
+  # Prepend all log lines with the following tags.
+  config.log_tags = [ :request_id ]
+
+  # Use a different cache store in production.
+  # config.cache_store = :mem_cache_store
+
+  # Use a real queuing backend for Active Job (and separate queues per environment).
+  # config.active_job.queue_adapter     = :resque
+  # config.active_job.queue_name_prefix = "myapp_production"
+
+  config.action_mailer.perform_caching = false
+
+  # Ignore bad email addresses and do not raise email delivery errors.
+  # Set this to true and configure the email server for immediate delivery to raise delivery errors.
+  # config.action_mailer.raise_delivery_errors = false
+
+  # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
+  # the I18n.default_locale when a translation cannot be found).
+  config.i18n.fallbacks = true
+
+  # Don't log any deprecations.
+  config.active_support.report_deprecations = false
+
+  # Use default logging formatter so that PID and timestamp are not suppressed.
+  config.log_formatter = ::Logger::Formatter.new
+
+  # Use a different logger for distributed setups.
+  # require "syslog/logger"
+  # config.logger = ActiveSupport::TaggedLogging.new(Syslog::Logger.new "app-name")
+
+  if ENV["RAILS_LOG_TO_STDOUT"].present?
+    logger           = ActiveSupport::Logger.new(STDOUT)
+    logger.formatter = config.log_formatter
+    config.logger    = ActiveSupport::TaggedLogging.new(logger)
+  end
+
+  # Do not dump schema after migrations.
+  config.active_record.dump_schema_after_migration = false
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/test.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/test.rb
new file mode 100644
index 000000000..6ea4d1e70
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/environments/test.rb
@@ -0,0 +1,60 @@
+require "active_support/core_ext/integer/time"
+
+# The test environment is used exclusively to run your application's
+# test suite. You never need to work with it otherwise. Remember that
+# your test database is "scratch space" for the test suite and is wiped
+# and recreated between test runs. Don't rely on the data there!
+
+Rails.application.configure do
+  # Settings specified here will take precedence over those in config/application.rb.
+
+  # Turn false under Spring and add config.action_view.cache_template_loading = true.
+  config.cache_classes = true
+
+  # Eager loading loads your whole application. When running a single test locally,
+  # this probably isn't necessary. It's a good idea to do in a continuous integration
+  # system, or in some way before deploying your code.
+  config.eager_load = ENV["CI"].present?
+
+  # Configure public file server for tests with Cache-Control for performance.
+  config.public_file_server.enabled = true
+  config.public_file_server.headers = {
+    "Cache-Control" => "public, max-age=#{1.hour.to_i}"
+  }
+
+  # Show full error reports and disable caching.
+  config.consider_all_requests_local       = true
+  config.action_controller.perform_caching = false
+  config.cache_store = :null_store
+
+  # Raise exceptions instead of rendering exception templates.
+  config.action_dispatch.show_exceptions = false
+
+  # Disable request forgery protection in test environment.
+  config.action_controller.allow_forgery_protection = false
+
+  # Store uploaded files on the local file system in a temporary directory.
+  config.active_storage.service = :test
+
+  config.action_mailer.perform_caching = false
+
+  # Tell Action Mailer not to deliver emails to the real world.
+  # The :test delivery method accumulates sent emails in the
+  # ActionMailer::Base.deliveries array.
+  config.action_mailer.delivery_method = :test
+
+  # Print deprecation notices to the stderr.
+  config.active_support.deprecation = :stderr
+
+  # Raise exceptions for disallowed deprecations.
+  config.active_support.disallowed_deprecation = :raise
+
+  # Tell Active Support which deprecation messages to disallow.
+  config.active_support.disallowed_deprecation_warnings = []
+
+  # Raises error for missing translations.
+  # config.i18n.raise_on_missing_translations = true
+
+  # Annotate rendered view with file names.
+  # config.action_view.annotate_rendered_view_with_filenames = true
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/importmap.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/importmap.rb
new file mode 100644
index 000000000..8dce42d40
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/importmap.rb
@@ -0,0 +1,7 @@
+# Pin npm packages by running ./bin/importmap
+
+pin "application", preload: true
+pin "@hotwired/turbo-rails", to: "turbo.min.js", preload: true
+pin "@hotwired/stimulus", to: "stimulus.min.js", preload: true
+pin "@hotwired/stimulus-loading", to: "stimulus-loading.js", preload: true
+pin_all_from "app/javascript/controllers", under: "controllers"
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/assets.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/assets.rb
new file mode 100644
index 000000000..2eeef966f
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/assets.rb
@@ -0,0 +1,12 @@
+# Be sure to restart your server when you modify this file.
+
+# Version of your assets, change this if you want to expire all your assets.
+Rails.application.config.assets.version = "1.0"
+
+# Add additional assets to the asset load path.
+# Rails.application.config.assets.paths << Emoji.images_path
+
+# Precompile additional assets.
+# application.js, application.css, and all non-JS/CSS in the app/assets
+# folder are already added.
+# Rails.application.config.assets.precompile += %w( admin.js admin.css )
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/content_security_policy.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/content_security_policy.rb
new file mode 100644
index 000000000..54f47cf15
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/content_security_policy.rb
@@ -0,0 +1,25 @@
+# Be sure to restart your server when you modify this file.
+
+# Define an application-wide content security policy.
+# See the Securing Rails Applications Guide for more information:
+# https://guides.rubyonrails.org/security.html#content-security-policy-header
+
+# Rails.application.configure do
+#   config.content_security_policy do |policy|
+#     policy.default_src :self, :https
+#     policy.font_src    :self, :https, :data
+#     policy.img_src     :self, :https, :data
+#     policy.object_src  :none
+#     policy.script_src  :self, :https
+#     policy.style_src   :self, :https
+#     # Specify URI for violation reports
+#     # policy.report_uri "/csp-violation-report-endpoint"
+#   end
+#
+#   # Generate session nonces for permitted importmap and inline scripts
+#   config.content_security_policy_nonce_generator = ->(request) { request.session.id.to_s }
+#   config.content_security_policy_nonce_directives = %w(script-src)
+#
+#   # Report violations without enforcing the policy.
+#   # config.content_security_policy_report_only = true
+# end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/filter_parameter_logging.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/filter_parameter_logging.rb
new file mode 100644
index 000000000..adc6568ce
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/filter_parameter_logging.rb
@@ -0,0 +1,8 @@
+# Be sure to restart your server when you modify this file.
+
+# Configure parameters to be filtered from the log file. Use this to limit dissemination of
+# sensitive information. See the ActiveSupport::ParameterFilter documentation for supported
+# notations and behaviors.
+Rails.application.config.filter_parameters += [
+  :passw, :secret, :token, :_key, :crypt, :salt, :certificate, :otp, :ssn
+]
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/inflections.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/inflections.rb
new file mode 100644
index 000000000..3860f659e
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/inflections.rb
@@ -0,0 +1,16 @@
+# Be sure to restart your server when you modify this file.
+
+# Add new inflection rules using the following format. Inflections
+# are locale specific, and you may define rules for as many different
+# locales as you wish. All of these examples are active by default:
+# ActiveSupport::Inflector.inflections(:en) do |inflect|
+#   inflect.plural /^(ox)$/i, "\\1en"
+#   inflect.singular /^(ox)en/i, "\\1"
+#   inflect.irregular "person", "people"
+#   inflect.uncountable %w( fish sheep )
+# end
+
+# These inflection rules are supported but not enabled by default:
+# ActiveSupport::Inflector.inflections(:en) do |inflect|
+#   inflect.acronym "RESTful"
+# end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/permissions_policy.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/permissions_policy.rb
new file mode 100644
index 000000000..00f64d71b
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/initializers/permissions_policy.rb
@@ -0,0 +1,11 @@
+# Define an application-wide HTTP permissions policy. For further
+# information see https://developers.google.com/web/updates/2018/06/feature-policy
+#
+# Rails.application.config.permissions_policy do |f|
+#   f.camera      :none
+#   f.gyroscope   :none
+#   f.microphone  :none
+#   f.usb         :none
+#   f.fullscreen  :self
+#   f.payment     :self, "https://secure.example.com"
+# end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/locales/en.yml b/serverside_challenge_1/challenges/MasafumiKondo07/config/locales/en.yml
new file mode 100644
index 000000000..8ca56fc74
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/locales/en.yml
@@ -0,0 +1,33 @@
+# Files in the config/locales directory are used for internationalization
+# and are automatically loaded by Rails. If you want to use locales other
+# than English, add the necessary files in this directory.
+#
+# To use the locales, use `I18n.t`:
+#
+#     I18n.t "hello"
+#
+# In views, this is aliased to just `t`:
+#
+#     <%= t("hello") %>
+#
+# To use a different locale, set it with `I18n.locale`:
+#
+#     I18n.locale = :es
+#
+# This would use the information in config/locales/es.yml.
+#
+# The following keys must be escaped otherwise they will not be retrieved by
+# the default I18n backend:
+#
+# true, false, on, off, yes, no
+#
+# Instead, surround them with single quotes.
+#
+# en:
+#   "true": "foo"
+#
+# To learn more, please read the Rails Internationalization guide
+# available at https://guides.rubyonrails.org/i18n.html.
+
+en:
+  hello: "Hello world"
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/puma.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/puma.rb
new file mode 100644
index 000000000..daaf03699
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/puma.rb
@@ -0,0 +1,43 @@
+# Puma can serve each request in a thread from an internal thread pool.
+# The `threads` method setting takes two numbers: a minimum and maximum.
+# Any libraries that use thread pools should be configured to match
+# the maximum value specified for Puma. Default is set to 5 threads for minimum
+# and maximum; this matches the default thread size of Active Record.
+#
+max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
+min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
+threads min_threads_count, max_threads_count
+
+# Specifies the `worker_timeout` threshold that Puma will use to wait before
+# terminating a worker in development environments.
+#
+worker_timeout 3600 if ENV.fetch("RAILS_ENV", "development") == "development"
+
+# Specifies the `port` that Puma will listen on to receive requests; default is 3000.
+#
+port ENV.fetch("PORT") { 3000 }
+
+# Specifies the `environment` that Puma will run in.
+#
+environment ENV.fetch("RAILS_ENV") { "development" }
+
+# Specifies the `pidfile` that Puma will use.
+pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
+
+# Specifies the number of `workers` to boot in clustered mode.
+# Workers are forked web server processes. If using threads and workers together
+# the concurrency of the application would be max `threads` * `workers`.
+# Workers do not work on JRuby or Windows (both of which do not support
+# processes).
+#
+# workers ENV.fetch("WEB_CONCURRENCY") { 2 }
+
+# Use the `preload_app!` method when specifying a `workers` number.
+# This directive tells Puma to first boot the application and load code
+# before forking the application. This takes advantage of Copy On Write
+# process behavior so workers use less memory.
+#
+# preload_app!
+
+# Allow puma to be restarted by `bin/rails restart` command.
+plugin :tmp_restart
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/routes.rb b/serverside_challenge_1/challenges/MasafumiKondo07/config/routes.rb
new file mode 100644
index 000000000..12c3ea802
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/routes.rb
@@ -0,0 +1,7 @@
+Rails.application.routes.draw do
+  namespace 'api' do
+    namespace 'v1' do
+      resources :electricity_charges_simulators
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/config/storage.yml b/serverside_challenge_1/challenges/MasafumiKondo07/config/storage.yml
new file mode 100644
index 000000000..4942ab669
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/config/storage.yml
@@ -0,0 +1,34 @@
+test:
+  service: Disk
+  root: <%= Rails.root.join("tmp/storage") %>
+
+local:
+  service: Disk
+  root: <%= Rails.root.join("storage") %>
+
+# Use bin/rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
+# amazon:
+#   service: S3
+#   access_key_id: <%= Rails.application.credentials.dig(:aws, :access_key_id) %>
+#   secret_access_key: <%= Rails.application.credentials.dig(:aws, :secret_access_key) %>
+#   region: us-east-1
+#   bucket: your_own_bucket-<%= Rails.env %>
+
+# Remember not to checkin your GCS keyfile to a repository
+# google:
+#   service: GCS
+#   project: your_project
+#   credentials: <%= Rails.root.join("path/to/gcs.keyfile") %>
+#   bucket: your_own_bucket-<%= Rails.env %>
+
+# Use bin/rails credentials:edit to set the Azure Storage secret (as azure_storage:storage_access_key)
+# microsoft:
+#   service: AzureStorage
+#   storage_account_name: your_account_name
+#   storage_access_key: <%= Rails.application.credentials.dig(:azure_storage, :storage_access_key) %>
+#   container: your_container_name-<%= Rails.env %>
+
+# mirror:
+#   service: Mirror
+#   primary: local
+#   mirrors: [ amazon, google, microsoft ]
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/basic_charges.csv b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/basic_charges.csv
new file mode 100644
index 000000000..72fa76156
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/basic_charges.csv
@@ -0,0 +1,23 @@
+plan_id,ampere,unit,price
+1,10,1,286.00
+1,15,1,429.00
+1,20,1,572.00
+1,30,1,858.00
+1,40,1,1144.00
+1,50,1,1430.00
+1,60,1,1716.00
+2,10,1,0.00
+2,15,1,0.00
+2,20,1,0.00
+2,30,1,0.00
+2,40,1,0.00
+2,50,1,0.00
+2,60,1,0.00
+3,30,1,858.00
+3,40,1,1144.00
+3,50,1,1430.00
+3,60,1,1716.00
+4,30,1,858.00
+4,40,1,1144.00
+4,50,1,1430.00
+4,60,1,1716.80
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/companies.csv b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/companies.csv
new file mode 100644
index 000000000..e2214e90e
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/companies.csv
@@ -0,0 +1,5 @@
+id,name
+1,東京電力エナジーパートナー
+2,Loopでんき
+3,東京ガス株式会社
+4,JXTGでんき
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/electricity_fees.csv b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/electricity_fees.csv
new file mode 100644
index 000000000..97ce2ca97
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/electricity_fees.csv
@@ -0,0 +1,12 @@
+plan_id,classification_min,classification_max,unit,price
+1,0,120,1,19.88
+1,121,300,1,26.48
+1,301,,1,30.57
+2,0,,1,26.40
+3,0,140,1,23.67
+3,141,350,1,23.88
+3,351,,1,26.41
+4,0,120,1,19.88
+4,121,300,1,26.48
+4,301,600,1,25.08
+4,601,,1,26.15
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/plans.csv b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/plans.csv
new file mode 100644
index 000000000..fcdb067d2
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/master_data_files/plans.csv
@@ -0,0 +1,5 @@
+company_id,name
+1,従量電灯B
+2,おうちプラン
+3,ずっとも電気1
+4,従量電灯Bたっぷりプラン
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915115835_create_companies.rb b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915115835_create_companies.rb
new file mode 100644
index 000000000..7838e5491
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915115835_create_companies.rb
@@ -0,0 +1,8 @@
+class CreateCompanies < ActiveRecord::Migration[7.0]
+  def change
+    create_table :companies do |t|
+      t.string :name, null: false
+      t.timestamps
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915120356_create_plans.rb b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915120356_create_plans.rb
new file mode 100644
index 000000000..5de48815c
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915120356_create_plans.rb
@@ -0,0 +1,10 @@
+class CreatePlans < ActiveRecord::Migration[7.0]
+  def change
+    create_table :plans do |t|
+      t.string :name, null: false
+      t.belongs_to :company, nul: false
+
+      t.timestamps
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915122810_create_electricity_fees.rb b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915122810_create_electricity_fees.rb
new file mode 100644
index 000000000..8433ba161
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915122810_create_electricity_fees.rb
@@ -0,0 +1,12 @@
+class CreateElectricityFees < ActiveRecord::Migration[7.0]
+  def change
+    create_table :electricity_fees do |t|
+      t.belongs_to :plan, nul: false
+      t.integer :classification_min, null: false
+      t.integer :classification_max
+      t.integer :unit, null: false
+      t.decimal :price, null: false, scale: 2, precision: 6
+      t.timestamps
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915122849_create_basic_charges.rb b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915122849_create_basic_charges.rb
new file mode 100644
index 000000000..88d838d67
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/migrate/20220915122849_create_basic_charges.rb
@@ -0,0 +1,11 @@
+class CreateBasicCharges < ActiveRecord::Migration[7.0]
+  def change
+    create_table :basic_charges do |t|
+      t.belongs_to :plan, nul: false
+      t.integer :ampere, null: false
+      t.integer :unit, null: false
+      t.decimal :price, null: false, scale: 2, precision: 6
+      t.timestamps
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/schema.rb b/serverside_challenge_1/challenges/MasafumiKondo07/db/schema.rb
new file mode 100644
index 000000000..e227ac53f
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/schema.rb
@@ -0,0 +1,49 @@
+# This file is auto-generated from the current state of the database. Instead
+# of editing this file, please use the migrations feature of Active Record to
+# incrementally modify your database, and then regenerate this schema definition.
+#
+# This file is the source Rails uses to define your schema when running `bin/rails
+# db:schema:load`. When creating a new database, `bin/rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
+#
+# It's strongly recommended that you check this file into your version control system.
+
+ActiveRecord::Schema[7.0].define(version: 2022_09_15_122849) do
+  create_table "basic_charges", charset: "utf8mb4", force: :cascade do |t|
+    t.bigint "plan_id"
+    t.integer "ampere", null: false
+    t.integer "unit", null: false
+    t.decimal "price", precision: 6, scale: 2, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["plan_id"], name: "index_basic_charges_on_plan_id"
+  end
+
+  create_table "companies", charset: "utf8mb4", force: :cascade do |t|
+    t.string "name", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+
+  create_table "electricity_fees", charset: "utf8mb4", force: :cascade do |t|
+    t.bigint "plan_id"
+    t.integer "classification_min", null: false
+    t.integer "classification_max"
+    t.integer "unit", null: false
+    t.decimal "price", precision: 6, scale: 2, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["plan_id"], name: "index_electricity_fees_on_plan_id"
+  end
+
+  create_table "plans", charset: "utf8mb4", force: :cascade do |t|
+    t.string "name", null: false
+    t.bigint "company_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["company_id"], name: "index_plans_on_company_id"
+  end
+
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/db/seeds.rb b/serverside_challenge_1/challenges/MasafumiKondo07/db/seeds.rb
new file mode 100644
index 000000000..96a4e3eb8
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/db/seeds.rb
@@ -0,0 +1,33 @@
+require "csv"
+
+CSV.foreach('db/master_data_files/companies.csv', headers: true) do |row|
+  Company.create(
+    name: row['name']
+  )
+end
+
+CSV.foreach('db/master_data_files/plans.csv', headers: true) do |row|
+  Plan.create(
+    company_id: row['company_id'],
+    name: row['name']
+  )
+end
+
+CSV.foreach('db/master_data_files/basic_charges.csv', headers: true) do |row|
+  BasicCharge.create(
+    plan_id: row['plan_id'],
+    ampere: row['ampere'],
+    unit: row['unit'],
+    price: row['price']
+  )
+end
+
+CSV.foreach('db/master_data_files/electricity_fees.csv', headers: true) do |row|
+  ElectricityFee.create(
+    plan_id: row['plan_id'],
+    classification_min: row['classification_min'],
+    classification_max: row['classification_max'],
+    unit: row['unit'],
+    price: row['price']
+  )
+end
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/docker-compose.yml b/serverside_challenge_1/challenges/MasafumiKondo07/docker-compose.yml
new file mode 100644
index 000000000..b5283044c
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/docker-compose.yml
@@ -0,0 +1,21 @@
+version: '3'
+services:
+  db:
+    image: mysql:5.7
+    environment:
+      MYSQL_ROOT_PASSWORD: password
+      MYSQL_DATABASE: root
+    ports:
+      - "3306:3306"
+    volumes:
+      - ./tmp/db:/var/lib/mysql
+
+  web:
+    build: .
+    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
+    volumes:
+      - .:/myapp
+    ports:
+      - "3000:3000"
+    depends_on:
+      - db
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/entrypoint.sh b/serverside_challenge_1/challenges/MasafumiKondo07/entrypoint.sh
new file mode 100644
index 000000000..0721cd7a5
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/entrypoint.sh
@@ -0,0 +1,8 @@
+#!/bin/bash
+set -e
+
+# Remove a potentially pre-existing server.pid for Rails.
+rm -f /myapp/tmp/pids/server.pid
+
+# Then exec the container's main process (what's set as CMD in the Dockerfile).
+exec "$@"
\ No newline at end of file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/lib/assets/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/lib/assets/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/lib/tasks/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/lib/tasks/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/log/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/log/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/404.html b/serverside_challenge_1/challenges/MasafumiKondo07/public/404.html
new file mode 100644
index 000000000..2be3af26f
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/public/404.html
@@ -0,0 +1,67 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>The page you were looking for doesn't exist (404)</title>
+  <meta name="viewport" content="width=device-width,initial-scale=1">
+  <style>
+  .rails-default-error-page {
+    background-color: #EFEFEF;
+    color: #2E2F30;
+    text-align: center;
+    font-family: arial, sans-serif;
+    margin: 0;
+  }
+
+  .rails-default-error-page div.dialog {
+    width: 95%;
+    max-width: 33em;
+    margin: 4em auto 0;
+  }
+
+  .rails-default-error-page div.dialog > div {
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #BBB;
+    border-top: #B00100 solid 4px;
+    border-top-left-radius: 9px;
+    border-top-right-radius: 9px;
+    background-color: white;
+    padding: 7px 12% 0;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+
+  .rails-default-error-page h1 {
+    font-size: 100%;
+    color: #730E15;
+    line-height: 1.5em;
+  }
+
+  .rails-default-error-page div.dialog > p {
+    margin: 0 0 1em;
+    padding: 1em;
+    background-color: #F7F7F7;
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #999;
+    border-bottom-left-radius: 4px;
+    border-bottom-right-radius: 4px;
+    border-top-color: #DADADA;
+    color: #666;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+  </style>
+</head>
+
+<body class="rails-default-error-page">
+  <!-- This file lives in public/404.html -->
+  <div class="dialog">
+    <div>
+      <h1>The page you were looking for doesn't exist.</h1>
+      <p>You may have mistyped the address or the page may have moved.</p>
+    </div>
+    <p>If you are the application owner check the logs for more information.</p>
+  </div>
+</body>
+</html>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/422.html b/serverside_challenge_1/challenges/MasafumiKondo07/public/422.html
new file mode 100644
index 000000000..c08eac0d1
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/public/422.html
@@ -0,0 +1,67 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>The change you wanted was rejected (422)</title>
+  <meta name="viewport" content="width=device-width,initial-scale=1">
+  <style>
+  .rails-default-error-page {
+    background-color: #EFEFEF;
+    color: #2E2F30;
+    text-align: center;
+    font-family: arial, sans-serif;
+    margin: 0;
+  }
+
+  .rails-default-error-page div.dialog {
+    width: 95%;
+    max-width: 33em;
+    margin: 4em auto 0;
+  }
+
+  .rails-default-error-page div.dialog > div {
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #BBB;
+    border-top: #B00100 solid 4px;
+    border-top-left-radius: 9px;
+    border-top-right-radius: 9px;
+    background-color: white;
+    padding: 7px 12% 0;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+
+  .rails-default-error-page h1 {
+    font-size: 100%;
+    color: #730E15;
+    line-height: 1.5em;
+  }
+
+  .rails-default-error-page div.dialog > p {
+    margin: 0 0 1em;
+    padding: 1em;
+    background-color: #F7F7F7;
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #999;
+    border-bottom-left-radius: 4px;
+    border-bottom-right-radius: 4px;
+    border-top-color: #DADADA;
+    color: #666;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+  </style>
+</head>
+
+<body class="rails-default-error-page">
+  <!-- This file lives in public/422.html -->
+  <div class="dialog">
+    <div>
+      <h1>The change you wanted was rejected.</h1>
+      <p>Maybe you tried to change something you didn't have access to.</p>
+    </div>
+    <p>If you are the application owner check the logs for more information.</p>
+  </div>
+</body>
+</html>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/500.html b/serverside_challenge_1/challenges/MasafumiKondo07/public/500.html
new file mode 100644
index 000000000..78a030af2
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/public/500.html
@@ -0,0 +1,66 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>We're sorry, but something went wrong (500)</title>
+  <meta name="viewport" content="width=device-width,initial-scale=1">
+  <style>
+  .rails-default-error-page {
+    background-color: #EFEFEF;
+    color: #2E2F30;
+    text-align: center;
+    font-family: arial, sans-serif;
+    margin: 0;
+  }
+
+  .rails-default-error-page div.dialog {
+    width: 95%;
+    max-width: 33em;
+    margin: 4em auto 0;
+  }
+
+  .rails-default-error-page div.dialog > div {
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #BBB;
+    border-top: #B00100 solid 4px;
+    border-top-left-radius: 9px;
+    border-top-right-radius: 9px;
+    background-color: white;
+    padding: 7px 12% 0;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+
+  .rails-default-error-page h1 {
+    font-size: 100%;
+    color: #730E15;
+    line-height: 1.5em;
+  }
+
+  .rails-default-error-page div.dialog > p {
+    margin: 0 0 1em;
+    padding: 1em;
+    background-color: #F7F7F7;
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #999;
+    border-bottom-left-radius: 4px;
+    border-bottom-right-radius: 4px;
+    border-top-color: #DADADA;
+    color: #666;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+  </style>
+</head>
+
+<body class="rails-default-error-page">
+  <!-- This file lives in public/500.html -->
+  <div class="dialog">
+    <div>
+      <h1>We're sorry, but something went wrong.</h1>
+    </div>
+    <p>If you are the application owner check the logs for more information.</p>
+  </div>
+</body>
+</html>
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/apple-touch-icon-precomposed.png b/serverside_challenge_1/challenges/MasafumiKondo07/public/apple-touch-icon-precomposed.png
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/apple-touch-icon.png b/serverside_challenge_1/challenges/MasafumiKondo07/public/apple-touch-icon.png
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/favicon.ico b/serverside_challenge_1/challenges/MasafumiKondo07/public/favicon.ico
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/public/robots.txt b/serverside_challenge_1/challenges/MasafumiKondo07/public/robots.txt
new file mode 100644
index 000000000..c19f78ab6
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/public/robots.txt
@@ -0,0 +1 @@
+# See https://www.robotstxt.org/robotstxt.html for documentation on how to use the robots.txt file
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/controllers/electricity_charges_simulators_controller_spec.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/controllers/electricity_charges_simulators_controller_spec.rb
new file mode 100644
index 000000000..5e7a01e9e
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/controllers/electricity_charges_simulators_controller_spec.rb
@@ -0,0 +1,61 @@
+require 'rails_helper'
+
+RSpec.describe Api::V1::ElectricityChargesSimulatorsController, type: :controller do
+  before do
+    company = FactoryBot.create(:company)
+    plan = FactoryBot.create(:plan, company_id: company.id)
+    FactoryBot.create(:basic_charge, plan_id: plan.id, ampere: 30, price: 858.00)
+    FactoryBot.create(:basic_charge, plan_id: plan.id, ampere: 40, price: 1144.00)
+    FactoryBot.create(:basic_charge, plan_id: plan.id, ampere: 50, price: 1430.00)
+    FactoryBot.create(:basic_charge, plan_id: plan.id, ampere: 60, price: 1716.00)
+    FactoryBot.create(:electricity_fee, plan_id: plan.id, classification_min: 0, classification_max: 120, price: 19.88)
+    FactoryBot.create(:electricity_fee, plan_id: plan.id, classification_min: 121, classification_max: 300, price: 26.48)
+    FactoryBot.create(:electricity_fee, plan_id: plan.id, classification_min: 301, classification_max: nil, price: 30.57)
+
+    second_company = FactoryBot.create(:company, name: "株式会社サンダー")
+    second_plan = FactoryBot.create(:plan, name: "テストサンダープラン", company_id: second_company.id)
+    FactoryBot.create(:basic_charge, plan_id: second_plan.id, ampere: 15, price: 429.00)
+    FactoryBot.create(:basic_charge, plan_id: second_plan.id, ampere: 30, price: 858.00)
+    FactoryBot.create(:basic_charge, plan_id: second_plan.id, ampere: 40, price: 1144.00)
+    FactoryBot.create(:basic_charge, plan_id: second_plan.id, ampere: 50, price: 1430.00)
+    FactoryBot.create(:basic_charge, plan_id: second_plan.id, ampere: 60, price: 1716.80)
+    FactoryBot.create(:electricity_fee, plan_id: second_plan.id, classification_min: 0, classification_max: 140, price: 23.67)
+    FactoryBot.create(:electricity_fee, plan_id: second_plan.id, classification_min: 141, classification_max: 350, price: 23.88)
+    FactoryBot.create(:electricity_fee, plan_id: second_plan.id, classification_min: 351, classification_max: nil, price: 26.41)
+  end
+
+  describe "GET /index" do
+
+    it "responds successfully" do
+      get :index, params: {ampere: 30, amount_used: 120}
+      expect(response).to have_http_status "200"
+    end
+
+    it "successfully return two plans" do
+      get :index, params: {ampere: 30, amount_used: 120}
+      plans = JSON.parse(response.body)
+      # 二件返却されていることを確認
+      expect(plans.length).to eq(2)
+
+      # 会社名、プラン名、価格が間違いないかそれぞれ確認
+      expect(plans[0]["company_name"]).to eq("テスト会社")
+      expect(plans[0]["plan_name"]).to eq("テストプラン")
+      # 基本料金(858.00) + 従量料金(19.88 * 120) = 3243.6
+      expect(plans[0]["price"]).to eq("3243.6")
+
+      expect(plans[1]["company_name"]).to eq("株式会社サンダー")
+      expect(plans[1]["plan_name"]).to eq("テストサンダープラン")
+      # 基本料金(858.00) + 従量料金(23.67 * 120) = 3698.4
+      expect(plans[1]["price"]).to eq("3698.4")
+    end
+
+    it "successfully return one plan" do
+      # 15Aの基本料金プランは２データのうち片方にしか存在しないため一件しか帰ってこないことを検証
+      get :index, params: {ampere: 15, amount_used: 120}
+      plans = JSON.parse(response.body)
+      # 一件のみ返却されていることを確認
+      expect(plans.length).to eq(1)
+    end
+
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/basic_charges.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/basic_charges.rb
new file mode 100644
index 000000000..875fea081
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/basic_charges.rb
@@ -0,0 +1,8 @@
+FactoryBot.define do
+  factory :basic_charge do
+    plan
+    ampere {}
+    unit { 1 }
+    price {}
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/companies.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/companies.rb
new file mode 100644
index 000000000..7b9aa83c3
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/companies.rb
@@ -0,0 +1,5 @@
+FactoryBot.define do
+  factory :company do
+    name {"テスト会社"}
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/electricity_fees.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/electricity_fees.rb
new file mode 100644
index 000000000..3447e1319
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/electricity_fees.rb
@@ -0,0 +1,9 @@
+FactoryBot.define do
+  factory :electricity_fee do
+    plan
+    classification_min {}
+    classification_max {}
+    unit { 1 }
+    price {}
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/plans.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/plans.rb
new file mode 100644
index 000000000..363444654
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/factories/plans.rb
@@ -0,0 +1,6 @@
+FactoryBot.define do
+  factory :plan do
+    company
+    name {"テストプラン"}
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/models/electricity_fee_spec.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/models/electricity_fee_spec.rb
new file mode 100644
index 000000000..5ef6e8f01
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/models/electricity_fee_spec.rb
@@ -0,0 +1,55 @@
+require 'rails_helper'
+
+RSpec.describe ElectricityFee, type: :model do
+  before do
+    company = FactoryBot.create(:company)
+    @plan = FactoryBot.create(:plan, company_id: company.id)
+    FactoryBot.create(:electricity_fee, plan_id: @plan.id, classification_min: 0, classification_max: 120, price: 19.88)
+    FactoryBot.create(:electricity_fee, plan_id: @plan.id, classification_min: 121, classification_max: 300, price: 26.48)
+    FactoryBot.create(:electricity_fee, plan_id: @plan.id, classification_min: 301, classification_max: nil, price: 30.57)
+  end
+
+  describe '#calc' do
+    context "60" do
+      # 19.88 * 60 = 1192.8
+      it "returns 1192.8" do
+        expect(ElectricityFee.calc(@plan, 60)).to eq(1192.8)
+      end
+    end
+
+    context "Boundary value 120" do
+      # 19.88 * 120 = 2385.6
+      it "returns 2385.6" do
+        expect(ElectricityFee.calc(@plan, 120)).to eq(2385.6)
+      end
+    end
+
+    context "Boundary value 121" do
+      # (19.88 * 120) + (26.48 * (121 - 120)) = 2412.08
+      it "returns 2412.08" do
+        expect(ElectricityFee.calc(@plan, 121)).to eq(2412.08)
+      end
+    end
+
+    context "Boundary value 300" do
+      # (19.88 * 120) + (26.48 * (300 - 120)) = 7152
+      it "returns 7152" do
+        expect(ElectricityFee.calc(@plan, 300)).to eq(7152)
+      end
+    end
+
+    context "Boundary value 301" do
+      # (19.88 * 120) + (26.48 * (300 - 120)) + (30.57 * (301 - 300)) = 7182.57
+      it "returns 7182.57" do
+        expect(ElectricityFee.calc(@plan, 301)).to eq(7182.57)
+      end
+    end
+
+    context "600" do
+      # (19.88 * 120) + (26.48 * (300 - 120)) + (30.57 * (600 - 300)) = 16323
+      it "returns 16323" do
+        expect(ElectricityFee.calc(@plan, 600)).to eq(16323)
+      end
+    end
+  end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/rails_helper.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/rails_helper.rb
new file mode 100644
index 000000000..e5be75d55
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/rails_helper.rb
@@ -0,0 +1,65 @@
+# This file is copied to spec/ when you run 'rails generate rspec:install'
+require 'spec_helper'
+ENV['RAILS_ENV'] ||= 'test'
+require_relative '../config/environment'
+# Prevent database truncation if the environment is production
+abort("The Rails environment is running in production mode!") if Rails.env.production?
+require 'rspec/rails'
+# Add additional requires below this line. Rails is not loaded until this point!
+
+# Requires supporting ruby files with custom matchers and macros, etc, in
+# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
+# run as spec files by default. This means that files in spec/support that end
+# in _spec.rb will both be required and run as specs, causing the specs to be
+# run twice. It is recommended that you do not name files matching this glob to
+# end with _spec.rb. You can configure this pattern with the --pattern
+# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
+#
+# The following line is provided for convenience purposes. It has the downside
+# of increasing the boot-up time by auto-requiring all files in the support
+# directory. Alternatively, in the individual `*_spec.rb` files, manually
+# require only the support files necessary.
+#
+# Dir[Rails.root.join('spec', 'support', '**', '*.rb')].sort.each { |f| require f }
+
+# Checks for pending migrations and applies them before tests are run.
+# If you are not using ActiveRecord, you can remove these lines.
+begin
+  ActiveRecord::Migration.maintain_test_schema!
+rescue ActiveRecord::PendingMigrationError => e
+  puts e.to_s.strip
+  exit 1
+end
+RSpec.configure do |config|
+  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
+  config.fixture_path = "#{::Rails.root}/spec/fixtures"
+
+  # If you're not using ActiveRecord, or you'd prefer not to run each of your
+  # examples within a transaction, remove the following line or assign false
+  # instead of true.
+  config.use_transactional_fixtures = true
+
+  # You can uncomment this line to turn off ActiveRecord support entirely.
+  # config.use_active_record = false
+
+  # RSpec Rails can automatically mix in different behaviours to your tests
+  # based on their file location, for example enabling you to call `get` and
+  # `post` in specs under `spec/controllers`.
+  #
+  # You can disable this behaviour by removing the line below, and instead
+  # explicitly tag your specs with their type, e.g.:
+  #
+  #     RSpec.describe UsersController, type: :controller do
+  #       # ...
+  #     end
+  #
+  # The different available types are documented in the features, such as in
+  # https://relishapp.com/rspec/rspec-rails/docs
+  config.infer_spec_type_from_file_location!
+
+  # Filter lines from Rails gems in backtraces.
+  config.filter_rails_from_backtrace!
+  # arbitrary gems may also be filtered via:
+  # config.filter_gems_from_backtrace("gem name")
+  config.include FactoryBot::Syntax::Methods
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/spec/spec_helper.rb b/serverside_challenge_1/challenges/MasafumiKondo07/spec/spec_helper.rb
new file mode 100644
index 000000000..a0d408059
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/spec/spec_helper.rb
@@ -0,0 +1,94 @@
+# This file was generated by the `rails generate rspec:install` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# The generated `.rspec` file contains `--require spec_helper` which will cause
+# this file to always be loaded, without a need to explicitly require it in any
+# files.
+#
+# Given that it is always loaded, you are encouraged to keep this file as
+# light-weight as possible. Requiring heavyweight dependencies from this file
+# will add to the boot time of your test suite on EVERY test run, even for an
+# individual file that may not need all of that loaded. Instead, consider making
+# a separate helper file that requires the additional dependencies and performs
+# the additional setup, and require it from the spec files that actually need
+# it.
+#
+# See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+# The settings below are suggested to provide a good initial experience
+# with RSpec, but feel free to customize to your heart's content.
+=begin
+  # This allows you to limit a spec run to individual examples or groups
+  # you care about by tagging them with `:focus` metadata. When nothing
+  # is tagged with `:focus`, all examples get run. RSpec also provides
+  # aliases for `it`, `describe`, and `context` that include `:focus`
+  # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  config.filter_run_when_matching :focus
+
+  # Allows RSpec to persist some state between runs in order to support
+  # the `--only-failures` and `--next-failure` CLI options. We recommend
+  # you configure your source control system to ignore this file.
+  config.example_status_persistence_file_path = "spec/examples.txt"
+
+  # Limits the available syntax to the non-monkey patched syntax that is
+  # recommended. For more details, see:
+  # https://relishapp.com/rspec/rspec-core/docs/configuration/zero-monkey-patching-mode
+  config.disable_monkey_patching!
+
+  # Many RSpec users commonly either run the entire suite or an individual
+  # file, and it's useful to allow more verbose output when running an
+  # individual spec file.
+  if config.files_to_run.one?
+    # Use the documentation formatter for detailed output,
+    # unless a formatter has already been configured
+    # (e.g. via a command-line flag).
+    config.default_formatter = "doc"
+  end
+
+  # Print the 10 slowest examples and example groups at the
+  # end of the spec run, to help surface which specs are running
+  # particularly slow.
+  config.profile_examples = 10
+
+  # Run specs in random order to surface order dependencies. If you find an
+  # order dependency and want to debug it, you can fix the order by providing
+  # the seed, which is printed after each run.
+  #     --seed 1234
+  config.order = :random
+
+  # Seed global randomization in this process using the `--seed` CLI option.
+  # Setting this allows you to use `--seed` to deterministically reproduce
+  # test failures related to randomization by passing the same `--seed` value
+  # as the one that triggered the failure.
+  Kernel.srand config.seed
+=end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/storage/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/storage/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/application_system_test_case.rb b/serverside_challenge_1/challenges/MasafumiKondo07/test/application_system_test_case.rb
new file mode 100644
index 000000000..d19212abd
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/test/application_system_test_case.rb
@@ -0,0 +1,5 @@
+require "test_helper"
+
+class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :chrome, screen_size: [1400, 1400]
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/channels/application_cable/connection_test.rb b/serverside_challenge_1/challenges/MasafumiKondo07/test/channels/application_cable/connection_test.rb
new file mode 100644
index 000000000..800405f15
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/test/channels/application_cable/connection_test.rb
@@ -0,0 +1,11 @@
+require "test_helper"
+
+class ApplicationCable::ConnectionTest < ActionCable::Connection::TestCase
+  # test "connects with cookies" do
+  #   cookies.signed[:user_id] = 42
+  #
+  #   connect
+  #
+  #   assert_equal connection.user_id, "42"
+  # end
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/controllers/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/controllers/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/fixtures/files/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/fixtures/files/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/helpers/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/helpers/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/integration/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/integration/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/mailers/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/mailers/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/models/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/models/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/system/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/test/system/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/test/test_helper.rb b/serverside_challenge_1/challenges/MasafumiKondo07/test/test_helper.rb
new file mode 100644
index 000000000..d713e377c
--- /dev/null
+++ b/serverside_challenge_1/challenges/MasafumiKondo07/test/test_helper.rb
@@ -0,0 +1,13 @@
+ENV["RAILS_ENV"] ||= "test"
+require_relative "../config/environment"
+require "rails/test_help"
+
+class ActiveSupport::TestCase
+  # Run tests in parallel with specified workers
+  parallelize(workers: :number_of_processors)
+
+  # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
+  fixtures :all
+
+  # Add more helper methods to be used by all tests here...
+end
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/tmp/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/tmp/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/tmp/pids/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/tmp/pids/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/tmp/storage/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/tmp/storage/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/vendor/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/vendor/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/serverside_challenge_1/challenges/MasafumiKondo07/vendor/javascript/.keep b/serverside_challenge_1/challenges/MasafumiKondo07/vendor/javascript/.keep
new file mode 100644
index 000000000..e69de29bb