backend/app/controllers/deerjikists_controller.rb

@@ -0,0 +1,17 @@
+class DeerjikistsController < ApplicationController
+  def show
+    platform = params[:platform].to_s.strip
+    code = params[:code].to_s.strip
+    return head :bad_request if platform.blank? || code.blank?
+
+    deerjikist = Deerjikist
+                 .joins(:tag)
+                 .includes(:tag, tag: :tag_name)
+                 .find_by(platform:, code:)
+    if deerjikist
+      render json: DeerjikistRepr.base(deerjikist)
+    else
+      head :not_found
+    end
+  end
+end

backend/app/controllers/tags_controller.rb

@@ -86,6 +86,27 @@ class TagsController < ApplicationController
     end
   end
 
+  def deerjikists
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(id: params[:id])
+    return head :bad_request unless tag
+
+    render json: DeerjikistRepr.many(tag.deerjikists)
+  end
+
+  def deerjikists_by_name
+    name = params[:name].to_s.strip
+    return head :bad_request if name.blank?
+
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(tag_names: { name: })
+    return head :not_found unless tag
+
+    render json: DeerjikistRepr.many(tag.deerjikists)
+  end
+
   def update
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.member?

backend/app/models/deerjikist.rb

@@ -0,0 +1,21 @@
+class Deerjikist < ApplicationRecord
+  self.primary_key = :platform, :code
+
+  belongs_to :tag
+
+  validates :platform, presence: true
+  validates :code, presence: true
+  validates :tag_id, presence: true
+
+  validate :tag_must_be_deerjikist
+
+  enum :platform, nico: 'nico', youtube: 'youtube'
+
+  private
+
+  def tag_must_be_deerjikist
+    if tag && !(tag.deerjikist?)
+      errors.add :tag, 'タグはニジラー・カテゴリである必要があります．'
+    end
+  end
+end

backend/app/models/tag.rb

@@ -24,6 +24,8 @@ class Tag < ApplicationRecord
 
   has_many :tag_similarities, dependent: :delete_all
 
+  has_many :deerjikists, dependent: :delete_all
+
   belongs_to :tag_name
   delegate :wiki_page, to: :tag_name
 
@@ -42,6 +44,7 @@ class Tag < ApplicationRecord
 
   validate :nico_tag_name_must_start_with_nico
   validate :tag_name_must_be_canonical
+  validate :category_must_be_deerjikist_with_deerjikists
 
   scope :nico_tags, -> { where(category: :nico) }
 
@@ -149,4 +152,10 @@ class Tag < ApplicationRecord
       errors.add :tag_name, 'tag_names へは実体を示す必要があります．'
     end
   end
+
+  def category_must_be_deerjikist_with_deerjikists
+    if !(deerjikist?) && deerjikists.exists?
+      errors.add :category, 'ニジラーと紐づいてゐるタグはニジラー・カテゴリである必要があります．'
+    end
+  end
 end

backend/app/representations/deerjikist_repr.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+
+module DeerjikistRepr
+  BASE = { only: [:platform, :code], include: { tag: TagRepr::BASE } }.freeze
+
+  module_function
+
+  def base deerjikist
+    deerjikist.as_json(BASE)
+  end
+
+  def many deerjikists
+    deerjikists.map { |d| base(d) }
+  end
+end

backend/config/routes.rb

@@ -9,7 +9,15 @@ Rails.application.routes.draw do
   resources :tags, only: [:index, :show, :update] do
     collection do
       get :autocomplete
-      get 'name/:name', action: :show_by_name
+
+      scope :name do
+        get ':name/deerjikists', action: :deerjikists_by_name
+        get ':name', action: :show_by_name
+      end
+    end
+
+    member do
+      get :deerjikists
     end
   end
 
@@ -54,4 +62,12 @@ Rails.application.routes.draw do
       post 'code/renew', action: :renew
     end
   end
+
+  resources :deerjikists, only: [] do
+    collection do
+      get ':platform/:code', action: :show
+      put ':platfrom/:code', action: :update
+      delete ':platform/:code', action: :destroy
+    end
+  end
 end

backend/db/migrate/20260303122700_create_deerjikists.rb

@@ -0,0 +1,10 @@
+class CreateDeerjikists < ActiveRecord::Migration[8.0]
+  def change
+    create_table :deerjikists, primary_key: [:platform, :code] do |t|
+      t.string :platform, null: false, limit: 16
+      t.string :code, null: false
+      t.references :tag, null: false
+      t.timestamps
+    end
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_01_27_005300) do
+ActiveRecord::Schema[8.0].define(version: 2026_03_03_122700) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -39,6 +39,15 @@ ActiveRecord::Schema[8.0].define(version: 2026_01_27_005300) do
     t.index ["blob_id", "variation_digest"], name: "index_active_storage_variant_records_uniqueness", unique: true
   end
 
+  create_table "deerjikists", primary_key: ["platform", "code"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "platform", limit: 16, null: false
+    t.string "code", null: false
+    t.bigint "tag_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["tag_id"], name: "index_deerjikists_on_tag_id"
+  end
+
   create_table "ip_addresses", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.binary "ip_address", limit: 16, null: false
     t.boolean "banned", default: false, null: false