diff --git a/backend/app/controllers/tags_controller.rb b/backend/app/controllers/tags_controller.rb
index d60d56d..13b71ba 100644
--- a/backend/app/controllers/tags_controller.rb
+++ b/backend/app/controllers/tags_controller.rb
@@ -770,31 +770,15 @@ class TagsController < ApplicationController
       TagVersioning.ensure_snapshot!(old_owner_tag, created_by_user: current_user)
     end
 
-    current_tag_name.wiki_page&.update!(tag_name_id: promoted_tag_name.id)
-    current_tag_name.association(:wiki_page).reset
-
-    current_tag_name.update!(canonical_id: promoted_tag_name.id,
-                             primary_flg: false, auto_generated: false)
-    promoted_tag_name.update!(tag:, canonical_id: nil, primary_flg: true, auto_generated: false)
-
-    TagName.where(tag:,
-                  language_code: current_tag_name.language_code,
-                  primary_flg: false)
-           .where.not(id: promoted_tag_name.id)
-           .find_each do |alias_tag_name|
-      alias_tag_name.update!(canonical_id: promoted_tag_name.id, primary_flg: false)
-    end
-
-    tag.update!(tag_name_id: promoted_tag_name.id)
-    current_tag_name.association(:wiki_page).reset
-    current_tag_name.association(:tag).reset
-    current_tag_name.reload.update!(canonical_id: promoted_tag_name.id, primary_flg: false)
+    current_tag_name&.update!(primary_flg: false, auto_generated: false)
+    promoted_tag_name.update!(tag:, primary_flg: true, auto_generated: false)
+    tag.association(:tag_names).reset
 
     return unless old_owner_tag && old_owner_tag != tag
 
     record_tag_version!(old_owner_tag.reload, event_type: :update,
                         created_by_user: current_user,
-                        language_code: current_tag_name.language_code)
+                        language_code: promoted_tag_name.language_code)
   end
 
   def update_aliases! locale, tag, alias_names
@@ -802,20 +786,15 @@ class TagsController < ApplicationController
 
     affected_tags = [tag]
 
-    primary_tag_name = TagName.find_by!(tag:,
-                                        language_code: locale.language_code,
-                                        primary_flg: true)
     current_aliases = tag.tag_names.where(language_code: locale.language_code,
                                           primary_flg: false).to_a
 
-    current_aliases.each do |alias_tag_name|
-      next if alias_names.include?(alias_tag_name.name)
-
-      affected_tags << alias_tag_name.tag
-    end
+    requested_aliases = TagName.where(
+        language_code: locale.language_code, name: alias_names)
+        .includes(:tag).index_by(&:name)
 
     alias_names.each do |alias_name|
-      alias_tag_name = TagName.find_by(language_code: locale.language_code, name: alias_name)
+      alias_tag_name = requested_aliases[alias_name]
       if alias_tag_name&.primary? && alias_tag_name.tag_id && alias_tag_name.tag_id != tag.id
         alias_tag_name.errors.add(:name, 'その名前は既に使はれてゐます．')
         raise ActiveRecord::RecordInvalid, alias_tag_name
@@ -831,16 +810,15 @@ class TagsController < ApplicationController
     current_aliases.each do |alias_tag_name|
       next if alias_names.include?(alias_tag_name.name)
 
-      alias_tag_name.update!(canonical_id: nil, tag_id: nil)
+      alias_tag_name.destroy!
     end
 
     alias_names.each do |alias_name|
-      alias_tag_name = TagName.find_or_initialize_by(
+      alias_tag_name = requested_aliases[alias_name] || TagName.new(
           language_code: locale.language_code,
           name: alias_name)
       alias_tag_name.script_code = locale.script_code
-      alias_tag_name.update!(tag:, primary_flg: false, auto_generated: false,
-                             canonical_id: primary_tag_name.id)
+      alias_tag_name.update!(tag:, primary_flg: false, auto_generated: false)
     end
 
     affected_tags.compact.uniq.each do |affected_tag|
diff --git a/backend/app/controllers/wiki_pages_controller.rb b/backend/app/controllers/wiki_pages_controller.rb
index 797c088..688fe7b 100644
--- a/backend/app/controllers/wiki_pages_controller.rb
+++ b/backend/app/controllers/wiki_pages_controller.rb
@@ -1,7 +1,7 @@
 class WikiPagesController < ApplicationController
   # 互換性のための Facade API
 
-  rescue_from Wiki::Commit::Conflict, with: :render_wiki_conflict
+  rescue_from TagDescriptionOperation::Conflict, with: :render_wiki_conflict
 
   def index
     title = params[:title].to_s.strip
@@ -38,7 +38,7 @@ class WikiPagesController < ApplicationController
     tag_group = TagGroup.find_by(id: params[:id])
     return render_tag_group tag_group if tag_group
 
-    render_wiki_page_or_404 nil
+    head :not_found
   end
 
   def show_by_title
@@ -55,7 +55,7 @@ class WikiPagesController < ApplicationController
 
     return render_wiki_page_by_tag_description tag_description if tag_description
 
-    render_wiki_page_or_404 nil
+    head :not_found
   end
 
   def exists
@@ -134,15 +134,15 @@ class WikiPagesController < ApplicationController
     if title.start_with?(TagGroupRepr::PREFIX)
       name = title.delete_prefix(TagGroupRepr::PREFIX)
       parsed = TagGroupMarkdownParser.parse(body:, group: nil)
-      group = TagGroupOperation.create!(name:, **parsed, actor: current_user,
-                                         require_compatibility: true)
+      group = TagGroupOperation.create!(
+          name:, **parsed.except(:compatibility_body), actor: current_user)
       version = current_group_version(group)
       return render_group_representation(TagGroupRepr.one(group), version,
                                          body: parsed.fetch(:compatibility_body),
                                          status: :created)
     end
 
-    page =
+    description =
         if title.include?(':')
           return render_unprocessable_entity field: :title
         else
@@ -153,7 +153,6 @@ class WikiPagesController < ApplicationController
               tag: tag_name.tag, body:, created_by_user: current_user, message:)
         end
 
-    description = TagDescription.find_by!(tag_id: page.tag_name.tag_id, language_code: 'ja')
     render json: WikiPageRepr.tag_description(description), status: :created
   rescue ActiveRecord::RecordInvalid => e
     render_validation_error e.record
@@ -179,22 +178,21 @@ class WikiPagesController < ApplicationController
 
       name = title.delete_prefix(TagGroupRepr::PREFIX)
       parsed = TagGroupMarkdownParser.parse(body:, group:)
-      TagGroupOperation.update!(group:, name:, **parsed, actor: current_user,
-                                require_compatibility: true)
+      TagGroupOperation.update!(
+          group:, name:, **parsed.except(:compatibility_body), actor: current_user)
       return head :ok
     end
 
     return render_unprocessable_entity field: :title if title.include?(':')
     description = TagDescription.find_by(id: params[:id])
     unless description
-      return render_unprocessable_entity field: :title if group || WikiPage.exists?(id: params[:id])
+      return render_unprocessable_entity field: :title if group
       return head :not_found
     end
     tag = description.tag
-    tag_name = TagDescriptionOperation.compatibility_tag_name(tag)
-    if tag_name.name.include?(':') || (group && title != tag_name.name)
-      return render_unprocessable_entity field: :title
-    end
+    tag_name = tag.tag_name('ja')
+    return render_unprocessable_entity field: :title unless tag_name
+    return render_unprocessable_entity field: :title if tag_name.name.include?(':')
 
     base_revision_id = params[:base_revision_id].presence
 
@@ -251,26 +249,6 @@ class WikiPagesController < ApplicationController
 
   private
 
-  def legacy_group_page? page
-    return false unless page
-    return true if page.title.start_with?(TagGroupRepr::PREFIX)
-
-    prefix = ApplicationRecord.sanitize_sql_like(TagGroupRepr::PREFIX)
-    page.wiki_versions.where('title LIKE ?', "#{ prefix }%").exists?
-  end
-
-  def legacy_update_identified? page, title, group
-    return false unless page
-    return true if page.title == title
-    return false if title == group.name
-
-    namespace = page.title.split(':', 2)
-    return true if namespace.size == 2 && title.start_with?("#{ namespace.first }:")
-
-    base = params[:base_revision_id].presence
-    base && page.wiki_revisions.exists?(id: base)
-  end
-
   def render_tag_group group
     version = if params[:version].present?
       group_version(group, params[:version])
@@ -357,27 +335,6 @@ class WikiPagesController < ApplicationController
     end
   end
 
-  def render_wiki_page_or_404 page
-    return head :not_found unless page
-
-    rev = find_revision(page)
-    return head :not_found unless rev
-
-    if rev.redirect?
-      return (
-          redirect_to wiki_page_by_title_path(title: rev.redirect_page.title),
-                      status: :moved_permanently)
-    end
-
-    body = rev.body
-    revision_id = rev.id
-    pred = page.pred_revision_id(revision_id)
-    succ = page.succ_revision_id(revision_id)
-    updated_at = rev.created_at
-
-    render json: WikiPageRepr.base(page).merge(body:, revision_id:, pred:, succ:, updated_at:)
-  end
-
   def render_wiki_page_by_tag_description description
     versions = description_versions(description)
     historical = params[:version].present?
@@ -432,14 +389,6 @@ class WikiPagesController < ApplicationController
     end
   end
 
-  def find_revision page
-    if params[:version].present?
-      page.wiki_revisions.find_by(id: params[:version])
-    else
-      page.current_revision
-    end
-  end
-
   def render_wiki_conflict err
     render json: { error: 'conflict', message: err.message }, status: :conflict
   end
diff --git a/backend/app/models/locale.rb b/backend/app/models/locale.rb
index 1d39f44..b06fab9 100644
--- a/backend/app/models/locale.rb
+++ b/backend/app/models/locale.rb
@@ -13,14 +13,13 @@ class Locale < ApplicationRecord
   def generate_tag_names!
     ApplicationRecord.transaction do
       tag_ids = TagName.where(language_code:, primary_flg: true).pluck(:tag_id)
-      Tag.where.not(id: tag_ids).find_each do
+      Tag.where.not(id: tag_ids).includes(:tag_names).find_each do
         TagName.create!(tag_id: _1.id,
                         language_code:,
                         name: TagName.generate_name(self, _1, _1.tag_name('ja')),
                         script_code:,
                         primary_flg: true,
-                        auto_generated: true,
-                        canonical_id: nil)
+                        auto_generated: true)
       end
     end
   end
diff --git a/backend/app/models/tag.rb b/backend/app/models/tag.rb
index 173a52a..9baa7e6 100644
--- a/backend/app/models/tag.rb
+++ b/backend/app/models/tag.rb
@@ -91,7 +91,6 @@ class Tag < ApplicationRecord
     end
   end
   def name(language_code) = tag_name(language_code)&.name
-  def wiki_page = tag_name('ja')&.wiki_page
 
   def system?
     tag_name('ja')&.name.in?(SYSTEM_TAG_NAMES)
@@ -260,16 +259,13 @@ class Tag < ApplicationRecord
       name = name.to_s.strip
 
       ApplicationRecord.transaction do
-        tn = TagName.find_or_create_by!(language_code:, name:) do
-          _1.script_code = locale.script_code
-          _1.primary_flg = true
-        end
+        tn = TagName.find_by(language_code:, name:)
+        next tn.tag if tn
 
-        tag = tn.tag
-        next tag if tag
-
-        tag = Tag.create!(tag_name_id: tn.id, category:)
-        tn.update!(tag:, primary_flg: true, canonical_id: nil, auto_generated: false)
+        tag = Tag.create!(category:)
+        tn = TagName.create!(tag:, language_code:, name:,
+                             script_code: locale.script_code, primary_flg: true,
+                             auto_generated: false)
         generate_tag_names!(locale, tag, tn)
         tag.association(:tag_names).reset
 
@@ -303,20 +299,17 @@ class Tag < ApplicationRecord
             end
           end
 
-          source_tag_name = source_tag.tag_name('ja')
-
-          if source_tag_name.wiki_page.present?
-            raise ActiveRecord::RecordInvalid.new(source_tag_name)
+          if source_tag.tag_descriptions.exists?
+            source_tag.errors.add(:base, :invalid)
+            raise ActiveRecord::RecordInvalid, source_tag
           end
 
           TagVersioning.record!(source_tag, event_type: :discard, created_by_user:)
           source_tag.tag_names.update_all(tag_id: target_tag.id, primary_flg: false,
+                                          auto_generated: false,
                                           updated_at: Time.current)
           source_tag.destroy!
 
-          source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
-                                         updated_at: Time.current)
-
           TagVersioning.record!(target_tag, event_type: :update, created_by_user:)
         end
 
@@ -376,8 +369,7 @@ class Tag < ApplicationRecord
                           name: TagName.generate_name(locale, tag, base_tag_name),
                           script_code:,
                           primary_flg: true,
-                          auto_generated: true,
-                          canonical_id: nil)
+                          auto_generated: true)
         end
       end
     end
diff --git a/backend/app/models/tag_name.rb b/backend/app/models/tag_name.rb
index 6c119ab..05b6b92 100644
--- a/backend/app/models/tag_name.rb
+++ b/backend/app/models/tag_name.rb
@@ -1,14 +1,12 @@
 class TagName < ApplicationRecord
   belongs_to :language, foreign_key: :language_code, primary_key: :code
-  belongs_to :tag, optional: true
-  has_one :wiki_page
+  belongs_to :tag
 
   validates :name, presence: true,
                    length: { maximum: 255 },
                    uniqueness: { scope: :language_code }
 
   validate :alias_name_must_not_have_prefix
-  validate :alias_must_not_have_wiki_page
   validate :name_must_be_sanitised
   validate :name_mustnt_start_with_nico
   validate :generated_name_must_be_reserved
@@ -21,14 +19,16 @@ class TagName < ApplicationRecord
 
     tns = TagName.where(language_code: locale.language_code, name: names).index_by(&:name)
 
+    primary_names = TagName.where(
+        language_code: locale.language_code, tag_id: tns.values.map(&:tag_id),
+        primary_flg: true).pluck(:tag_id, :name).to_h
+
     names.map { |name|
       tag_name = tns[name]
-      if !tag_name || tag_name.primary? || tag_name.tag_id.nil?
+      if !tag_name || tag_name.primary?
         name
       else
-        TagName.find_by(language_code: locale.language_code,
-                        tag_id: tag_name.tag_id,
-                        primary_flg: true)&.name || name
+        primary_names[tag_name.tag_id] || name
       end
     }.uniq
   end
@@ -53,12 +53,6 @@ class TagName < ApplicationRecord
     end
   end
 
-  def alias_must_not_have_wiki_page
-    if !(primary?) && wiki_page
-      errors.add :primary_flg, 'Wiki 参照がある名前はエーリアスになれません．'
-    end
-  end
-
   def name_must_be_sanitised
     if name? && name != TagNameSanitisationRule.sanitise(name)
       errors.add :name, '名前に使用できない文字が含まれてゐます．'
diff --git a/backend/app/models/tag_name_sanitisation_rule.rb b/backend/app/models/tag_name_sanitisation_rule.rb
index 4731d4f..b853f00 100644
--- a/backend/app/models/tag_name_sanitisation_rule.rb
+++ b/backend/app/models/tag_name_sanitisation_rule.rb
@@ -33,13 +33,7 @@ class TagNameSanitisationRule < ApplicationRecord
               existing_tag = existing_tn.tag
               source_tag = tn.tag
 
-              if existing_tag
-                Tag.merge_tags!(existing_tag, source_tag) if tn.tag
-              elsif source_tag
-                tn.update_columns(tag_id: nil, updated_at: Time.current)
-                source_tag.update_columns(tag_name_id: existing_tn.id, updated_at: Time.current)
-                existing_tn.update_columns(tag_id: source_tag.id, updated_at: Time.current)
-              end
+              Tag.merge_tags!(existing_tag, source_tag) if existing_tag != source_tag
               tn.destroy!
 
               next
diff --git a/backend/app/models/user.rb b/backend/app/models/user.rb
index 59b076c..3b0b87b 100644
--- a/backend/app/models/user.rb
+++ b/backend/app/models/user.rb
@@ -13,10 +13,10 @@ class User < ApplicationRecord
   has_many :ip_addresses, through: :user_ips
   has_many :user_post_views, dependent: :destroy
   has_many :viewed_posts, through: :user_post_views, source: :post
-  has_many :created_wiki_pages,
-           class_name: 'WikiPage', foreign_key: :created_user_id, dependent: :nullify
-  has_many :updated_wiki_pages,
-           class_name: 'WikiPage', foreign_key: :updated_user_id, dependent: :nullify
+  has_many :created_tag_descriptions, class_name: 'TagDescription',
+           foreign_key: :created_by_user_id, dependent: :nullify
+  has_many :updated_tag_descriptions, class_name: 'TagDescription',
+           foreign_key: :updated_by_user_id, dependent: :nullify
 
   def viewed?(post) = user_post_views.exists?(post_id: post.id)
 
diff --git a/backend/app/models/wiki_line.rb b/backend/app/models/wiki_line.rb
deleted file mode 100644
index b9c3465..0000000
--- a/backend/app/models/wiki_line.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-class WikiLine < ApplicationRecord
-  has_many :wiki_revision_lines, dependent: :restrict_with_exception
-
-  validates :sha256, presence: true, uniqueness: true, length: { is: 64 }
-  validates :body, presence: true
-
-  def self.upsert_by_body! body
-    sha = Digest::SHA256.hexdigest(body)
-    now = Time.current
-
-    upsert(sha256: sha, body:, created_at: now, updated_at: now)
-
-    find_by!(sha256: sha)
-  end
-end
diff --git a/backend/app/models/wiki_page.rb b/backend/app/models/wiki_page.rb
deleted file mode 100644
index caee630..0000000
--- a/backend/app/models/wiki_page.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-require 'set'
-
-
-class WikiPage < ApplicationRecord
-  include MyDiscard
-
-  has_many :wiki_revisions, dependent: :destroy
-  belongs_to :created_user, class_name: 'User'
-  belongs_to :updated_user, class_name: 'User'
-
-  has_many :redirected_from_revisions,
-           class_name: 'WikiRevision',
-           foreign_key: :redirect_page_id,
-           dependent: :nullify
-
-  has_many :wiki_versions
-
-  attribute :version_no, :integer, default: 1
-
-  belongs_to :tag_name
-  validates :tag_name, presence: true
-  validates :body, presence: true
-
-  def title = tag_name.name
-  def deprecated_at = tag_name.tag&.deprecated_at
-
-  def title= val
-    (self.tag_name ||= build_tag_name).name = val
-  end
-
-  def current_revision = wiki_revisions.order(id: :desc).first
-
-  def resolve_redirect limit: 10
-    page = self
-    visited = Set.new
-
-    limit.times do
-      return page if visited.include?(page.id)
-
-      visited.add(page.id)
-
-      rev = page.current_revision
-      return page if !(rev&.redirect?) || !(rev.redirect_page)
-
-      page = rev.redirect_page
-    end
-
-    page
-  end
-
-  def pred_revision_id revision_id
-    wiki_revisions.where('id < ?', revision_id).order(id: :desc).limit(1).pick(:id)
-  end
-
-  def succ_revision_id revision_id
-    wiki_revisions.where('id > ?', revision_id).order(id: :asc).limit(1).pick(:id)
-  end
-end
diff --git a/backend/app/models/wiki_revision.rb b/backend/app/models/wiki_revision.rb
deleted file mode 100644
index 3e0781a..0000000
--- a/backend/app/models/wiki_revision.rb
+++ /dev/null
@@ -1,55 +0,0 @@
-class WikiRevision < ApplicationRecord
-  belongs_to :wiki_page
-  belongs_to :base_revision, class_name: 'WikiRevision', optional: true
-  belongs_to :created_user, class_name: 'User'
-  belongs_to :redirect_page, class_name: 'WikiPage', optional: true
-
-  has_many :wiki_revision_lines, dependent: :delete_all
-  has_many :wiki_lines, through: :wiki_revision_lines
-
-  enum :kind, content: 0, redirect: 1
-
-  validates :kind, presence: true
-  validates :lines_count, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
-  validates :tree_sha256, length: { is: 64 }, allow_nil: true
-
-  validate :kind_consistency
-
-  def body
-    return unless content?
-
-    wiki_revision_lines
-        .includes(:wiki_line)
-        .order(:position)
-        .map { |rev| rev.wiki_line.body }
-        .join("\n")
-  end
-
-  private
-
-  def kind_consistency
-    if content?
-      if tree_sha256.blank?
-        errors.add(:tree_sha256, '種類がページの場合は必須です．') 
-      end
-
-      if redirect_page_id.present?
-        errors.add(:redirect_page_id, '種類がページの場合は空である必要があります．')
-      end
-    end
-
-    if redirect?
-      if redirect_page_id.blank?
-        errors.add(:redirect_page_id, '種類がリダイレクトの場合は必須です．')
-      end
-
-      if tree_sha256.present?
-        errors.add(:tree_sha256, '種類がリダイレクトの場合は空である必要があります．')
-      end
-
-      if lines_count.to_i > 0
-        errors.add(:lines_count, '種類がリダイレクトの場合は 0 である必要があります．')
-      end
-    end
-  end
-end
diff --git a/backend/app/models/wiki_revision_line.rb b/backend/app/models/wiki_revision_line.rb
deleted file mode 100644
index 8d58642..0000000
--- a/backend/app/models/wiki_revision_line.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-class WikiRevisionLine < ApplicationRecord
-  belongs_to :wiki_revision
-  belongs_to :wiki_line
-
-  validates :position, presence: true,
-                       numericality: { only_integer: true, greater_than_or_equal_to: 0 }
-  validates :position, uniqueness: { scope: :wiki_revision_id }
-end
diff --git a/backend/app/models/wiki_version.rb b/backend/app/models/wiki_version.rb
deleted file mode 100644
index 4f55804..0000000
--- a/backend/app/models/wiki_version.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-class WikiVersion < ApplicationRecord
-  include VersionRecord
-
-  belongs_to :wiki_page
-
-  validates :title, presence: true
-  validates :body, presence: true
-end
diff --git a/backend/app/representations/wiki_page_repr.rb b/backend/app/representations/wiki_page_repr.rb
index e1b780e..2c747ba 100644
--- a/backend/app/representations/wiki_page_repr.rb
+++ b/backend/app/representations/wiki_page_repr.rb
@@ -2,14 +2,8 @@
 
 
 module WikiPageRepr
-  BASE = { methods: [:title, :deprecated_at] }.freeze
-
   module_function
 
-  def base wiki_page
-    wiki_page.as_json(BASE)
-  end
-
   def tag_description description
     tag = description.tag
     { 'id' => description.id,
@@ -29,8 +23,4 @@ module WikiPageRepr
   def tag_group tag_group
     TagGroupRepr.tag_group(tag_group).merge('resource_type' => 'tag_group')
   end
-
-  def many wiki_pages
-    wiki_pages.map { |p| base(p) }
-  end
 end
diff --git a/backend/app/services/tag_description_operation.rb b/backend/app/services/tag_description_operation.rb
index c0d0d11..69020dd 100644
--- a/backend/app/services/tag_description_operation.rb
+++ b/backend/app/services/tag_description_operation.rb
@@ -1,18 +1,20 @@
 class TagDescriptionOperation
   LANGUAGE_CODE = 'ja'
 
+  class Conflict < StandardError
+    ;
+  end
+
   def self.create!(tag:, body:, created_by_user:, message: nil)
     ApplicationRecord.transaction do
       tag.lock!
       raise ActiveRecord::RecordNotUnique if TagDescription.exists?(
           tag_id: tag.id, language_code: LANGUAGE_CODE)
 
-      page = Wiki::CompatibilityWriter.create!(
-          tag_name: compatibility_tag_name(tag), body:, created_by_user:, message:)
-      revision = page.wiki_revisions.order(id: :desc).first
-      record_version!(tag:, revision:, body: revision.body, user: created_by_user,
-                      description: nil)
-      page
+      description = TagDescription.new(tag:, language_code: LANGUAGE_CODE)
+      body = normalise_body!(description, body)
+      record_version!(description:, body:, user: created_by_user)
+      description
     end
   end
 
@@ -22,51 +24,47 @@ class TagDescriptionOperation
       tag.lock!
       description = TagDescription.lock.find_by!(
           tag_id: tag.id, language_code: LANGUAGE_CODE)
-      tag_name = compatibility_tag_name(tag)
-      page = WikiPage.lock.find_by(tag_name_id: tag_name.id)
-      unless page
-        versions = TagDescriptionVersion.where(tag_id: tag.id, language_code: LANGUAGE_CODE)
-        if base_revision_id.present? && versions.maximum(:id) != base_revision_id.to_i
-          raise Wiki::Commit::Conflict, '競合が発生してゐます．'
-        end
-        page = Wiki::CompatibilityWriter.create!(
-            tag_name:, body:, created_by_user: updated_by_user, message:)
-        revision = page.current_revision
-        record_version!(tag:, revision:, body: revision.body,
-                        user: updated_by_user, description:)
-        next revision
+      body = normalise_body!(description, body)
+      latest = TagDescriptionVersion.find_by(
+          tag_id: tag.id, language_code: LANGUAGE_CODE,
+          version_no: description.version_no)
+      if base_revision_id.present? && latest&.id != base_revision_id.to_i
+        raise Conflict, '競合が発生してゐます．'
       end
-      revision = Wiki::CompatibilityWriter.update!(
-          page:, body:, updated_by_user:, message:,
-          base_revision_id:)
-      next unless revision
+      next if latest && normalise_body(description.body) == body
 
-      record_version!(tag:, revision:, body: revision.body,
-                      user: updated_by_user, description:)
-      revision
+      record_version!(description:, body:, user: updated_by_user)
     end
   end
 
-  def self.compatibility_tag_name tag
-    tag.tag_name(LANGUAGE_CODE) || TagName.find_by!(id: tag.tag_name_id,
-                                                  language_code: LANGUAGE_CODE)
+  def self.record_version! description:, body:, user:
+    creating = description.new_record?
+    version_no = creating ? 1 : description.version_no + 1
+    version = TagDescriptionVersion.create!(
+        tag_id: description.tag_id, language_code: description.language_code,
+        version_no:, event_type: creating ? 'create' : 'update', body:,
+        source_language_code: description.source_language_code,
+        source_version_no: description.source_version_no,
+        created_by_user_id: user.id, created_at: Time.current)
+    description.created_by_user_id = user.id if creating
+    description.update!(body:, version_no:, updated_by_user_id: user.id)
+    version
   end
-
-  def self.record_version! tag:, revision:, body:, user:, description:
-    version_no = description ? description.version_no + 1 : 1
-    TagDescriptionVersion.create!(
-        id: revision.id, tag_id: tag.id, language_code: LANGUAGE_CODE,
-        version_no:, event_type: description ? 'update' : 'create', body:,
-        created_by_user_id: user.id, created_at: revision.created_at)
-    if description
-      description.update!(body:, version_no:, updated_by_user_id: user.id)
-    else
-      TagDescription.create!(
-          tag_id: tag.id,
-          language_code: LANGUAGE_CODE, version_no:, body:,
-          created_by_user_id: user.id, updated_by_user_id: user.id)
-    end
-  end
-
   private_class_method :record_version!
+
+  def self.normalise_body body
+    body.to_s.gsub(/\r\n?/, "\n")
+        .encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
+        .sub(/\n+\z/, '')
+  end
+  private_class_method :normalise_body
+
+  def self.normalise_body! description, body
+    normalised = normalise_body(body)
+    return normalised if normalised.present?
+
+    description.errors.add(:body, :blank)
+    raise ActiveRecord::RecordInvalid, description
+  end
+  private_class_method :normalise_body!
 end
diff --git a/backend/app/services/tag_group_operation.rb b/backend/app/services/tag_group_operation.rb
index 985276e..b565486 100644
--- a/backend/app/services/tag_group_operation.rb
+++ b/backend/app/services/tag_group_operation.rb
@@ -1,10 +1,8 @@
 class TagGroupOperation
   MAX_PLACEMENT_DEPTH = 5
-  PREFIX = TagGroupRepr::PREFIX
 
-  def self.create!(name:, description:, members:, placements:, actor:,
-                   require_compatibility: false, compatibility_body: nil)
-    group, sync_issue = ApplicationRecord.transaction do
+  def self.create!(name:, description:, members:, placements:, actor:)
+    ApplicationRecord.transaction do
       group = TagGroup.new(version_no: 1, created_by_user: actor,
                            updated_by_user: actor)
       attributes = prepare!(group:, name:, description:, members:, placements:)
@@ -13,21 +11,15 @@ class TagGroupOperation
       group.save!
       persist_structure!(group:, attributes:, actor:)
       persist_version!(group:, attributes:, actor:, event_type: 'create')
-      issue = sync_compatibility!(group:, actor:, old_name: nil,
-                                  require_compatibility:, compatibility_body:)
-      [group, issue]
+      group
     end
-    report_sync_issue(group, actor, sync_issue)
-    group
   end
 
-  def self.update!(group:, name:, description:, members:, placements:, actor:,
-                   require_compatibility: false, compatibility_body: nil)
-    group, sync_issue = ApplicationRecord.transaction do
+  def self.update!(group:, name:, description:, members:, placements:, actor:)
+    ApplicationRecord.transaction do
       group.lock!
-      old_name = group.name
       attributes = prepare!(group:, name:, description:, members:, placements:)
-      next [group, nil] if unchanged?(group, attributes)
+      next group if unchanged?(group, attributes)
 
       group.update!(name: attributes.fetch(:name),
                     description: attributes.fetch(:description),
@@ -35,12 +27,8 @@ class TagGroupOperation
                     updated_by_user: actor)
       persist_structure!(group:, attributes:, actor:)
       persist_version!(group:, attributes:, actor:, event_type: 'update')
-      issue = sync_compatibility!(group:, actor:, old_name:,
-                                  require_compatibility:, compatibility_body:)
-      [group, issue]
+      group
     end
-    report_sync_issue(group, actor, sync_issue)
-    group
   end
 
   def self.prepare!(group:, name:, description:, members:, placements:)
@@ -313,57 +301,6 @@ class TagGroupOperation
   end
   private_class_method :persist_version!
 
-  def self.sync_compatibility!(group:, actor:, old_name:,
-                               require_compatibility:, compatibility_body:)
-    representation = TagGroupRepr.one(group)
-    body = begin
-      TagGroupMarkdownRenderer.render(representation)
-    rescue TagGroupMarkdownRenderer::UnsupportedStructure => error
-      if compatibility_body.present?
-        compatibility_body
-      elsif require_compatibility
-        invalid!(group, :base, error.message)
-      else
-        return error.message
-      end
-    end
-    invalid!(group, :base, '本文は必須です．') if body.blank?
-
-    title = "#{ PREFIX }#{ group.name }"
-    old_title = old_name && "#{ PREFIX }#{ old_name }"
-    page = if old_title
-      WikiPage.joins(:tag_name).find_by(tag_names: { name: old_title })
-    else
-      nil
-    end
-    page ||= WikiPage.joins(:tag_name).find_by(tag_names: { name: title })
-
-    if page
-      tag_name = page.tag_name
-      tag_name.update!(name: title) if tag_name.name != title
-      Wiki::Commit.legacy_content!(page:, body:, created_user: actor, message: nil,
-                                   base_revision_id: nil)
-    else
-      tag_name = TagName.find_or_initialize_by(language_code: 'ja', name: title)
-      tag_name.script_code = 'Jpan'
-      tag_name.primary_flg = true
-      tag_name.auto_generated = false
-      tag_name.save!
-      Wiki::CompatibilityWriter.create!(tag_name:, body:, created_by_user: actor)
-    end
-    nil
-  end
-  private_class_method :sync_compatibility!
-
-  def self.report_sync_issue(group, actor, reason)
-    return unless reason
-
-    payload = { status: 'unsupported_structure', tag_group_id: group.id,
-                version_no: group.version_no, user_id: actor&.id, reason: }
-    Rails.logger.warn("tag_group_wiki_sync_skipped #{ payload.to_json }")
-  end
-  private_class_method :report_sync_issue
-
   def self.placement_references(nodes)
     nodes.flat_map do |node|
       own = if node.key?('tag_id')
diff --git a/backend/app/services/wiki/commit.rb b/backend/app/services/wiki/commit.rb
deleted file mode 100644
index d18bd63..0000000
--- a/backend/app/services/wiki/commit.rb
+++ /dev/null
@@ -1,164 +0,0 @@
-require 'digest'
-
-
-module Wiki
-  class Commit
-    class Conflict < StandardError
-      ;
-    end
-
-    def self.create_content! tag_name:, body:, created_by_user:, message: nil
-      if tag_name.tag && tag_name.language_code == 'ja' && !tag_name.name.include?(':')
-        return TagDescriptionOperation.create!(
-            tag: tag_name.tag, body:, created_by_user:, message:)
-      end
-
-      tag_name.errors.add(:base, :invalid)
-      raise ActiveRecord::RecordInvalid, tag_name
-    end
-
-    def self.create_legacy_content! tag_name:, body:, created_by_user:, message: nil
-      normalised = normalise_body(body)
-
-      page = WikiPage.new(tag_name:,
-                          body: normalised,
-                          created_user: created_by_user,
-                          updated_user: created_by_user)
-
-      if normalised.blank?
-        page.errors.add(:body, :blank)
-        raise ActiveRecord::RecordInvalid, page
-      end
-
-      ActiveRecord::Base.transaction do
-        page.save!
-
-        new(page:, created_user: created_by_user).content!(
-            body: normalised,
-            message:,
-            base_revision_id: nil)
-
-        page
-      end
-    end
-
-    def self.content! page:, body:, created_user:, message: nil, base_revision_id: nil
-      description = TagDescription.find_by(tag_id: page.tag_name.tag_id, language_code: 'ja')
-      description ||= TagDescription.joins(:tag).find_by(
-          tags: { tag_name_id: page.tag_name_id }, language_code: 'ja')
-      if description && !page.title.include?(':')
-        return TagDescriptionOperation.update!(
-            tag: description.tag, body:, updated_by_user: created_user,
-            message:, base_revision_id:)
-      end
-
-      page.errors.add(:base, :invalid)
-      raise ActiveRecord::RecordInvalid, page
-    end
-
-    def self.legacy_content! page:, body:, created_user:, message: nil,
-                             base_revision_id: nil
-      new(page:, created_user:).content!(body:, message:, base_revision_id:)
-    end
-
-    def self.redirect! page:, redirect_page:, created_user:, message: nil, base_revision_id: nil
-      new(page:, created_user:).redirect!(redirect_page:, message:, base_revision_id:)
-    end
-
-    def initialize page:, created_user:
-      @page = page
-      @created_user = created_user
-    end
-
-    def content! body:, message:, base_revision_id:
-      normalised = self.class.normalise_body(body)
-      if normalised.blank?
-        @page.errors.add(:body, :blank)
-        raise ActiveRecord::RecordInvalid, @page
-      end
-
-      lines = split_lines(normalised)
-
-      line_shas = lines.map { |line| Digest::SHA256.hexdigest(line) }
-      tree_sha = Digest::SHA256.hexdigest(line_shas.join(','))
-
-      ActiveRecord::Base.transaction do
-        @page.lock!
-
-        if base_revision_id.present?
-          current_id = @page.wiki_revisions.maximum(:id)
-          if current_id && current_id != base_revision_id.to_i
-            raise Conflict,
-                "競合が発生してゐます" +
-                "（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
-          end
-        end
-
-        line_id_by_sha = upsert_lines!(lines, line_shas)
-        line_ids = line_shas.map { |sha| line_id_by_sha.fetch(sha) }
-        @page.update!(body: normalised)
-
-        WikiVersionRecorder.record!(
-            page: @page,
-            event_type: @page.wiki_versions.exists? ? :update : :create,
-            reason: message,
-            created_by_user: @created_user)
-
-        rev = WikiRevision.create!(
-            wiki_page:        @page,
-            base_revision_id:,
-            created_user:     @created_user,
-            kind:             :content,
-            redirect_page_id: nil,
-            message:,
-            lines_count:      lines.length,
-            tree_sha256:      tree_sha)
-
-        rows = line_ids.each_with_index.map do |line_id, pos|
-          { wiki_revision_id: rev.id, wiki_line_id: line_id, position: pos }
-        end
-        WikiRevisionLine.insert_all!(rows) if rows.any?
-        rev
-      end
-    end
-
-    def redirect!(redirect_page:, message:, base_revision_id:) = raise '廃止しました．'
-
-    def self.normalise_body body
-      s = body.to_s
-      s.gsub!(/\r\n?/, "\n")
-      s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
-      s.gsub(/\n+$/, '')
-    end
-
-    private
-
-    def split_lines(body) = body.split("\n")
-
-    def upsert_lines! lines, line_shas
-      now = Time.current
-
-      id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
-
-      missing_by_sha = { }
-
-      line_shas.each_with_index do |sha, i|
-        next if id_by_sha.key?(sha)
-        next if missing_by_sha.key?(sha)
-
-        missing_by_sha[sha] = {
-            sha256:     sha,
-            body:       lines[i],
-            created_at: now,
-            updated_at: now }
-      end
-
-      if missing_by_sha.any?
-        WikiLine.upsert_all(missing_by_sha.values)
-        id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
-      end
-
-      id_by_sha
-    end
-  end
-end
diff --git a/backend/app/services/wiki/compatibility_writer.rb b/backend/app/services/wiki/compatibility_writer.rb
deleted file mode 100644
index c7bcaa1..0000000
--- a/backend/app/services/wiki/compatibility_writer.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-module Wiki
-  class CompatibilityWriter
-    def self.create! tag_name:, body:, created_by_user:, message: nil
-      ApplicationRecord.transaction do
-        tag_name.lock!
-        page = WikiPage.lock.find_by(tag_name_id: tag_name.id)
-        if page
-          update!(page:, body:, updated_by_user: created_by_user, message:)
-          page
-        else
-          Commit.create_legacy_content!(tag_name:, body:, created_by_user:, message:)
-        end
-      end
-    end
-
-    def self.update! page:, body:, updated_by_user:, message: nil,
-                     base_revision_id: nil
-      normalised = Commit.normalise_body(body)
-      if normalised.blank?
-        return Commit.legacy_content!(
-            page:, body: normalised, created_user: updated_by_user, message:,
-            base_revision_id:)
-      end
-
-      if base_revision_id.present?
-        current_id = page.wiki_revisions.maximum(:id)
-        if current_id && current_id != base_revision_id.to_i
-          raise Commit::Conflict,
-              "競合が発生してゐます" +
-              "（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
-        end
-      end
-
-      if Commit.normalise_body(page.body) == normalised && page.wiki_revisions.exists?
-        return
-      end
-
-      Commit.legacy_content!(
-          page:, body: normalised, created_user: updated_by_user, message:,
-          base_revision_id:)
-    end
-  end
-end
diff --git a/backend/app/services/wiki_version_recorder.rb b/backend/app/services/wiki_version_recorder.rb
deleted file mode 100644
index 41e1db9..0000000
--- a/backend/app/services/wiki_version_recorder.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-class WikiVersionRecorder < VersionRecorder
-  def self.record! page:, event_type:, reason: nil, created_by_user:
-    new(page:, event_type:, reason:, created_by_user:).record!
-  end
-
-  def initialize page:, event_type:, reason: nil, created_by_user:
-    @reason = reason
-    super(record: page, event_type:, created_by_user:)
-  end
-
-  private
-
-  def version_class = WikiVersion
-  def version_association = :wiki_versions
-  def record_key = :wiki_page
-
-  def snapshot_attributes = {
-      title: @record.title,
-      body: @record.body,
-      reason: @reason }
-end