diff --git a/backend/app/models/tag.rb b/backend/app/models/tag.rb
index fe9c9a1..fd49e10 100644
--- a/backend/app/models/tag.rb
+++ b/backend/app/models/tag.rb
@@ -48,7 +48,7 @@ class Tag < ApplicationRecord
   validate :tag_name_must_be_canonical
   validate :category_must_be_deerjikist_with_deerjikists
 
-  scope :nico_tags, -> { where(category: :nico) }
+  scope :nico_tags, -> { nico }
 
   CATEGORY_PREFIXES = {
       'general:'    => :general,
@@ -97,14 +97,12 @@ class Tag < ApplicationRecord
       pf, cat = CATEGORY_PREFIXES.find { |p, _| name.downcase.start_with?(p) } || ['', nil]
       name = TagName.canonicalise(name.sub(/\A#{ pf }/i, '')).first
       find_or_create_by_tag_name!(name, category: (cat || :general)).tap do |tag|
-        if cat && tag.category != cat
-          tag.update!(category: cat)
-        end
+        tag.update!(category: cat) if cat && tag.category != cat
       end
     end
 
     tags << Tag.tagme if with_tagme && tags.size < 10 && tags.none?(Tag.tagme)
-    tags << Tag.no_deerjikist if tags.all? { |t| t.category != 'deerjikist' }
+    tags << Tag.no_deerjikist if tags.all? { |t| !(t.deerjikist?) }
     tags.uniq(&:id)
   end
 
@@ -166,19 +164,20 @@ class Tag < ApplicationRecord
         tag_name.reload
         tag_name.update!(canonical: target_tag.tag_name)
       end
-    end
 
-    target_tag.update!(post_count: PostTag.kept.where(tag: target_tag).count)
+      # 再集計
+      target_tag.update_columns(post_count: PostTag.kept.where(tag: target_tag).count)
+    end
 
-    target_tag
+    target_tag.reload
   end
 
   private
 
   def nico_tag_name_must_start_with_nico
     n = name.to_s
-    if ((category == 'nico' && !(n.downcase.start_with?('nico:'))) || 
-        (category != 'nico' && n.downcase.start_with?('nico:')))
+    if ((nico? && !(n.downcase.start_with?('nico:'))) || 
+        (!(nico?) && n.downcase.start_with?('nico:')))
       errors.add :name, 'ニコニコ・タグの命名規則に反してゐます．'
     end
   end