diff --git a/backend/app/controllers/tags_controller.rb b/backend/app/controllers/tags_controller.rb
index ffa3527..baf0e7e 100644
--- a/backend/app/controllers/tags_controller.rb
+++ b/backend/app/controllers/tags_controller.rb
@@ -26,7 +26,11 @@ class TagsController < ApplicationController
 
   def show
     tag = Tag.find_by(id: params[:id])
-    render json: tag.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
+    if tag
+      render json: tag.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
+    else
+      head :not_found
+    end
   end
 
   def show_by_name
diff --git a/backend/config/application.rb b/backend/config/application.rb
index 14b74b9..24390bd 100644
--- a/backend/config/application.rb
+++ b/backend/config/application.rb
@@ -11,6 +11,7 @@ module Backend
     # Initialize configuration defaults for originally generated Rails version.
     config.load_defaults 8.0
 
+    config.i18n.available_locales = [:ja, :en]
     config.i18n.default_locale = :ja
 
     # Please, add to the `ignore` list any other `lib` subdirectories that do
diff --git a/backend/config/locales/ja.yml b/backend/config/locales/ja.yml
new file mode 100644
index 0000000..47cf834
--- /dev/null
+++ b/backend/config/locales/ja.yml
@@ -0,0 +1,2 @@
+ja:
+  hello: 'ぬ゛〜゛ん゛'
diff --git a/backend/spec/factories/wiki_pages.rb b/backend/spec/factories/wiki_pages.rb
new file mode 100644
index 0000000..b4f1496
--- /dev/null
+++ b/backend/spec/factories/wiki_pages.rb
@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :wiki_page do
+    title { "TestPage" }
+    association :created_user, factory: :user
+    association :updated_user, factory: :user
+  end
+end
diff --git a/backend/spec/rails_helper.rb b/backend/spec/rails_helper.rb
index 22122cb..480f4cb 100644
--- a/backend/spec/rails_helper.rb
+++ b/backend/spec/rails_helper.rb
@@ -39,6 +39,10 @@ rescue ActiveRecord::PendingMigrationError => e
   abort e.to_s.strip
 end
 RSpec.configure do |config|
+  config.before do
+    I18n.locale = :en
+  end
+
   config.include TestRecords
 
   # FactoryBot の create / create_list を使へるやぅにする