diff --git a/app/models/memo.rb b/app/models/memo.rb
index 610a7684d..4dc153c81 100644
--- a/app/models/memo.rb
+++ b/app/models/memo.rb
@@ -1,7 +1,9 @@
 class Memo < ApplicationRecord
   include Searchable::Memo
 
-  has_many :memo_tag_repertoires, :dependent => :destroy
+  belongs_to :forum, touch: true
+
+  has_many :memo_tag_repertoires, dependent: :destroy
   has_many :tag_repertoires, :through => :memo_tag_repertoires
 
   has_many :praise_tread, as: :praise_tread_object, dependent: :destroy
diff --git a/db/migrate/20190730070155_create_forums.rb b/db/migrate/20190730070155_create_forums.rb
deleted file mode 100644
index f1f6eb96a..000000000
--- a/db/migrate/20190730070155_create_forums.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-class CreateForums < ActiveRecord::Migration[5.2]
-  def change
-    create_table :forums do |t|
-
-      t.timestamps
-    end
-  end
-end