diff --git a/backend/app/controllers/nico_tags_controller.rb b/backend/app/controllers/nico_tags_controller.rb
index da3d831..2b28175 100644
--- a/backend/app/controllers/nico_tags_controller.rb
+++ b/backend/app/controllers/nico_tags_controller.rb
@@ -6,11 +6,11 @@ class NicoTagsController < ApplicationController
     cursor = params[:cursor].presence
 
     q = Tag.nico_tags
-           .includes(:tag_name, linked_tags: :tag_name)
+           .includes(:tag_name, tag_name: :wiki_page, linked_tags: { tag_name: :wiki_page })
            .order(updated_at: :desc)
     q = q.where('tags.updated_at < ?', Time.iso8601(cursor)) if cursor
 
-    tags = q.limit(limit + 1)
+    tags = q.limit(limit + 1).to_a
 
     next_cursor = nil
     if tags.size > limit
diff --git a/backend/app/controllers/posts_controller.rb b/backend/app/controllers/posts_controller.rb
index 57340eb..eb4dee6 100644
--- a/backend/app/controllers/posts_controller.rb
+++ b/backend/app/controllers/posts_controller.rb
@@ -17,16 +17,17 @@ class PostsController < ApplicationController
         'posts.created_at)'
     q =
         filtered_posts
-        .preload(tags: :tag_name)
+        .preload(tags: { tag_name: :wiki_page })
         .with_attached_thumbnail
         .select("posts.*, #{ sort_sql } AS sort_ts")
         .order(Arel.sql("#{ sort_sql } DESC"))
-    posts = (
+    posts =
         if cursor
           q.where("#{ sort_sql } < ?", Time.iso8601(cursor)).limit(limit + 1)
         else
           q.limit(limit).offset(offset)
-        end).to_a
+        end
+        .to_a
 
     next_cursor = nil
     if cursor && posts.length > limit
@@ -52,7 +53,9 @@ class PostsController < ApplicationController
   end
 
   def random
-    post = filtered_posts.preload(tags: :tag_name).order('RAND()').first
+    post = filtered_posts.preload(tags: { tag_name: :wiki_page })
+                         .order('RAND()')
+                         .first
     return head :not_found unless post
 
     viewed = current_user&.viewed?(post) || false
@@ -64,7 +67,7 @@ class PostsController < ApplicationController
   end
 
   def show
-    post = Post.includes(tags: :tag_name).find(params[:id])
+    post = Post.includes(tags: { tag_name: :wiki_page }).find(params[:id])
     return head :not_found unless post
 
     viewed = current_user&.viewed?(post) || false
@@ -151,7 +154,7 @@ class PostsController < ApplicationController
   end
 
   def changes
-    id = params[:id]
+    id = params[:id].presence
     page = (params[:page].presence || 1).to_i
     limit = (params[:limit].presence || 20).to_i
 
@@ -162,30 +165,34 @@ class PostsController < ApplicationController
 
     pts = PostTag.with_discarded
     pts = pts.where(post_id: id) if id.present?
-    pts = pts.includes(:post, { tag: :tag_name }, :created_user, :deleted_user)
+    pts = pts.includes(:post, :created_user, :deleted_user,
+                       tag: { tag_name: :wiki_page })
 
     events = []
     pts.each do |pt|
+      tag = pt.tag.as_json(only: [:id, :category], methods: [:name, :has_wiki])
+      post = pt.post
+
       events << Event.new(
-          post:         pt.post,
-          tag:          pt.tag.as_json(only: [:id, :category], methods: [:name, :has_wiki]),
-          user:         pt.created_user && { id: pt.created_user.id, name: pt.created_user.name },
-          change_type:  'add',
-          timestamp:    pt.created_at)
+          post:,
+          tag:,
+          user: pt.created_user && { id: pt.created_user.id, name: pt.created_user.name },
+          change_type: 'add',
+          timestamp: pt.created_at)
 
       if pt.discarded_at
         events << Event.new(
-            post:         pt.post,
-            tag:          pt.tag.as_json(only: [:id, :category], methods: [:name, :has_wiki]),
-            user:         pt.deleted_user && { id: pt.deleted_user.id, name: pt.deleted_user.name },
-            change_type:  'remove',
-            timestamp:    pt.discarded_at)
+            post:,
+            tag:,
+            user: pt.deleted_user && { id: pt.deleted_user.id, name: pt.deleted_user.name },
+            change_type: 'remove',
+            timestamp: pt.discarded_at)
       end
     end
     events.sort_by!(&:timestamp)
     events.reverse!
 
-    render json: { changes: events.slice(offset, limit).as_json, count: events.size }
+    render json: { changes: (events.slice(offset, limit) || []).as_json, count: events.size }
   end
 
   private
diff --git a/backend/app/controllers/tags_controller.rb b/backend/app/controllers/tags_controller.rb
index 1c5dcb2..5251e72 100644
--- a/backend/app/controllers/tags_controller.rb
+++ b/backend/app/controllers/tags_controller.rb
@@ -4,10 +4,14 @@ class TagsController < ApplicationController
 
     tags =
         if post_id.present?
-          Tag.joins(:posts).where(posts: { id: post_id })
+          Tag.joins(:posts, :tag_name)
         else
-          Tag.all
+          Tag.joins(:tag_name)
         end
+        .includes(:tag_name, tag_name: :wiki_page)
+    if post_id.present?
+      tags = tags.where(posts: { id: post_id })
+    end
 
     render json: tags.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
   end
@@ -33,7 +37,8 @@ class TagsController < ApplicationController
       matched_alias_by_tag_name_id[canonical_id] ||= alias_name
     end
 
-    base = Tag.joins(:tag_name).includes(:tag_name)
+    base = Tag.joins(:tag_name)
+              .includes(:tag_name, tag_name: :wiki_page)
     base = base.where('tags.post_count > 0') if present_only
 
     canonical_hit =
@@ -58,7 +63,9 @@ class TagsController < ApplicationController
   end
 
   def show
-    tag = Tag.find_by(id: params[:id])
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(id: params[:id])
     if tag
       render json: tag.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
     else
@@ -70,7 +77,9 @@ class TagsController < ApplicationController
     name = params[:name].to_s.strip
     return head :bad_request if name.blank?
 
-    tag = Tag.joins(:tag_name).includes(:tag_name).find_by(tag_names: { name: })
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(tag_names: { name: })
     if tag
       render json: tag.as_json(only: [:id, :category, :post_count], methods: [:name, :has_wiki])
     else
diff --git a/backend/app/controllers/wiki_pages_controller.rb b/backend/app/controllers/wiki_pages_controller.rb
index 20b2912..6dc4216 100644
--- a/backend/app/controllers/wiki_pages_controller.rb
+++ b/backend/app/controllers/wiki_pages_controller.rb
@@ -3,7 +3,11 @@ class WikiPagesController < ApplicationController
 
   def index
     title = params[:title].to_s.strip
-    return render json: WikiPage.all.as_json(methods: [:title]) if title.blank?
+    if title.blank?
+      return render json: WikiPage.joins(:tag_name)
+                                  .includes(:tag_name)
+                                  .as_json(methods: [:title])
+    end
 
     q = WikiPage.joins(:tag_name).includes(:tag_name)
         .where('tag_names.name LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%")
@@ -11,7 +15,9 @@ class WikiPagesController < ApplicationController
   end
 
   def show
-    page = WikiPage.find_by(id: params[:id])
+    page = WikiPage.joins(:tag_name)
+                   .includes(:tag_name)
+                   .find_by(id: params[:id])
     render_wiki_page_or_404 page
   end
 
@@ -19,7 +25,7 @@ class WikiPagesController < ApplicationController
     title = params[:title].to_s.strip
     page = WikiPage.joins(:tag_name)
                    .includes(:tag_name)
-                   .find_by(tag_names: { name: title })
+                   .find_by(tag_name: { name: title })
     render_wiki_page_or_404 page
   end
 
@@ -47,7 +53,7 @@ class WikiPagesController < ApplicationController
     from = params[:from].presence
     to = params[:to].presence
 
-    page = WikiPage.find(id)
+    page = WikiPage.joins(:tag_name).includes(:tag_name).find(id)
 
     from_rev = from && page.wiki_revisions.find(from)
     to_rev = to ? page.wiki_revisions.find(to) : page.current_revision
@@ -131,7 +137,9 @@ class WikiPagesController < ApplicationController
 
   def changes
     id = params[:id].presence
-    q = WikiRevision.includes(:wiki_page, :created_user).order(id: :desc)
+    q = WikiRevision.joins(wiki_page: :tag_name)
+                    .includes(:created_user, wiki_page: :tag_name)
+                    .order(id: :desc)
     q = q.where(wiki_page_id: id) if id
 
     render json: q.limit(200).map { |rev|
@@ -139,7 +147,7 @@ class WikiPagesController < ApplicationController
         pred:         rev.base_revision_id,
         succ:         nil,
         wiki_page:    { id: rev.wiki_page_id, title: rev.wiki_page.title },
-        user:         { id: rev.created_user.id, name: rev.created_user.name },
+        user:         rev.created_user && { id: rev.created_user.id, name: rev.created_user.name },
         kind:         rev.kind,
         message:      rev.message,
         timestamp:    rev.created_at }
diff --git a/backend/app/models/post.rb b/backend/app/models/post.rb
index e25575f..c898615 100644
--- a/backend/app/models/post.rb
+++ b/backend/app/models/post.rb
@@ -30,13 +30,15 @@ class Post < ApplicationRecord
     super(options).merge(thumbnail: nil)
   end
 
-  def related(limit: nil)
-    ids = post_similarities.select(:target_post_id).order(cos: :desc)
+  def related limit: nil
+    ids = post_similarities.order(cos: :desc)
     ids = ids.limit(limit) if limit
     ids = ids.pluck(:target_post_id)
-    return [] if ids.empty?
+    return Post.none if ids.empty?
 
-    Post.where(id: ids).order(Arel.sql("FIELD(id, #{ ids.join(',') })"))
+    Post.where(id: ids)
+        .with_attached_thumbnail
+        .order(Arel.sql("FIELD(posts.id, #{ ids.join(',') })"))
   end
 
   def resized_thumbnail!
diff --git a/backend/app/models/tag.rb b/backend/app/models/tag.rb
index c4b36e6..60cc79b 100644
--- a/backend/app/models/tag.rb
+++ b/backend/app/models/tag.rb
@@ -25,6 +25,8 @@ class Tag < ApplicationRecord
   has_many :tag_similarities, dependent: :delete_all
 
   belongs_to :tag_name
+  delegate :wiki_page, to: :tag_name
+
   delegate :name, to: :tag_name, allow_nil: true
   validates :tag_name, presence: true
 
@@ -56,7 +58,7 @@ class Tag < ApplicationRecord
   end
 
   def has_wiki
-    tag_name&.wiki_page.present?
+    wiki_page.present?
   end
 
   def self.tagme