diff --git a/backend/db/migrate/20260919000000_create_languages.rb b/backend/db/migrate/20260919000000_create_languages.rb
new file mode 100644
index 0000000..e9f1887
--- /dev/null
+++ b/backend/db/migrate/20260919000000_create_languages.rb
@@ -0,0 +1,20 @@
+class CreateLanguages < ActiveRecord::Migration[8.0]
+  def up
+    create_table :languages, id: { type: :string, limit: 16 }, primary_key: :code do |t|
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        languages(code, name, created_at)
+      VALUES
+        ('ja', '日本語', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :languages
+  end
+end
diff --git a/backend/db/migrate/20260919010000_create_scripts.rb b/backend/db/migrate/20260919010000_create_scripts.rb
new file mode 100644
index 0000000..1ebb5ac
--- /dev/null
+++ b/backend/db/migrate/20260919010000_create_scripts.rb
@@ -0,0 +1,20 @@
+class CreateScripts < ActiveRecord::Migration[8.0]
+  def up
+    create_table :scripts, id: { type: 'CHAR(4)' }, primary_key: :code do |t|
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        scripts(code, name, created_at)
+      VALUES
+        ('Jpan', '漢字および仮名文字', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :scripts
+  end
+end
diff --git a/backend/db/migrate/20260919020000_create_locales.rb b/backend/db/migrate/20260919020000_create_locales.rb
new file mode 100644
index 0000000..afcd475
--- /dev/null
+++ b/backend/db/migrate/20260919020000_create_locales.rb
@@ -0,0 +1,25 @@
+class CreateLocales < ActiveRecord::Migration[8.0]
+  def up
+    create_table :locales, id: { type: :string, limit: 32 }, primary_key: :code do |t|
+      t.string :language_code, limit: 16, null: false, index: true
+      t.column :script_code, 'CHAR(4)', null: false
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+
+      t.foreign_key :languages, column: :language_code, primary_key: :code
+      t.foreign_key :scripts, column: :script_code, primary_key: :code
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        locales(code, language_code, script_code, name, created_at)
+      VALUES
+        ('ja', 'ja', 'Jpan', '日本語', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :locales
+  end
+end
diff --git a/backend/db/migrate/20260919030000_add_columns_to_tag_names.rb b/backend/db/migrate/20260919030000_add_columns_to_tag_names.rb
new file mode 100644
index 0000000..c0e3784
--- /dev/null
+++ b/backend/db/migrate/20260919030000_add_columns_to_tag_names.rb
@@ -0,0 +1,28 @@
+class AddColumnsToTagNames < ActiveRecord::Migration[8.0]
+  def up
+    add_column :tag_names, :language_code, :string,
+               limit: 16, null: false, after: :id, default: 'ja'
+    add_column :tag_names, :script_code, 'CHAR(4)',
+               null: false, after: :name, default: 'Jpan'
+
+    add_foreign_key :tag_names, :languages, column: :language_code, primary_key: :code
+    add_foreign_key :tag_names, :scripts, column: :script_code, primary_key: :code
+
+    remove_index :tag_names, :name
+    add_index :tag_names, [:language_code, :name], unique: true
+
+    change_column_default :tag_names, :language_code, from: 'ja', to: nil
+    change_column_default :tag_names, :script_code, from: 'Jpan', to: nil
+  end
+
+  def down
+    remove_foreign_key :tag_names, column: :language_code
+    remove_foreign_key :tag_names, column: :script_code
+
+    remove_index :tag_names, [:language_code, :name]
+    add_index :tag_names, :name, unique: true
+
+    remove_column :tag_names, :script_code
+    remove_column :tag_names, :language_code
+  end
+end