diff --git a/backend/lib/tasks/sync_nico.rake b/backend/lib/tasks/sync_nico.rake
index 97af101..d6e4f92 100644
--- a/backend/lib/tasks/sync_nico.rake
+++ b/backend/lib/tasks/sync_nico.rake
@@ -2,6 +2,16 @@ namespace :nico do
   desc 'ニコニコ DB 同期'
   task sync: :environment do
     require 'open3'
+    require 'open-uri'
+    require 'nokogiri'
+
+    fetch_thumbnail = -> url {
+      html = URI.open(url, read_timeout: 60, 'User-Agent' => 'Mozilla/5.0').read
+      doc = Nokogiri::HTML(html)
+
+      doc.at('meta[name="thumbnail"]')&.[]('content').presence
+    }
+
     mysql_user = ENV['MYSQL_USER']
     mysql_pass = ENV['MYSQL_PASS']
     nizika_nico_path = ENV['NIZIKA_NICO_PATH']
@@ -18,18 +28,39 @@ namespace :nico do
         unless post
           title = datum['title']
           url = "https://www.nicovideo.jp/watch/#{ datum['code'] }"
-          post = Post.new(title:, url:, thumbnail_base: '', uploaded_user: nil)
+          thumbnail_base = fetch_thumbnail.(url) || '' rescue ''
+          post = Post.new(title:, url:, thumbnail_base:, uploaded_user: nil)
+          if thumbnail_base.present?
+            post.thumbnail.attach(
+                io:           URI.open(thumbnail_base),
+                filename:     File.basename(URI.parse(thumbnail_base).path),
+                content_type: 'image/jpeg')
+          end
           post.save!
+          post.resized_thumbnail!
         end
 
-        post.tags.destroy(post.tags.where(category: 'nico'))
-        datum['tags'].each do |name|
-          name = "nico:#{ name }"
-          tag = Tag.find_or_initialize_by(name:, category: 'nico')
-          post.tags << tag
+        current_tags = post.tags.where(category: 'nico').pluck(:name).sort
+        new_tags = datum['tags'].map { |tag| "nico:#{ tag }" }.sort
+        if current_tags != new_tags
+          post.tags.destroy(post.tags.where(name: current_tags))
+          new_tags.each do |name|
+            post.tags << Tag.find_or_initialize_by(name:, category: 'nico')
+          end
+          if post.tags.size < 20
+            name = 'タグ希望'
+            post.tags.destroy(post.tags.find_by(name:))
+            post.tags << Tag.find_or_initialize_by(name:) { |tag|
+              tag.category = 'meta'
+            }
+          end
+          name = 'bot操作'
+          post.tags.destroy(post.tags.find_by(name:))
+          post.tags << Tag.find_or_initialize_by(name:) { |tag|
+            tag.category = 'meta'
+          }
         end
       end
     end
   end
 end
-