diff --git a/app/models/grid_weapon.rb b/app/models/grid_weapon.rb
index c24dcbe..afbb8ea 100644
--- a/app/models/grid_weapon.rb
+++ b/app/models/grid_weapon.rb
@@ -11,6 +11,7 @@ class GridWeapon < ApplicationRecord
   belongs_to :weapon_key1, class_name: 'WeaponKey', foreign_key: :weapon_key1_id, optional: true
   belongs_to :weapon_key2, class_name: 'WeaponKey', foreign_key: :weapon_key2_id, optional: true
   belongs_to :weapon_key3, class_name: 'WeaponKey', foreign_key: :weapon_key3_id, optional: true
+  belongs_to :weapon_key4, class_name: 'WeaponKey', foreign_key: :weapon_key4_id, optional: true
 
   belongs_to :awakening, optional: true
 
diff --git a/db/migrate/20240113180227_add_weapon_key_4_to_grid_weapon.rb b/db/migrate/20240113180227_add_weapon_key_4_to_grid_weapon.rb
new file mode 100644
index 0000000..ea7c03e
--- /dev/null
+++ b/db/migrate/20240113180227_add_weapon_key_4_to_grid_weapon.rb
@@ -0,0 +1,5 @@
+class AddWeaponKey4ToGridWeapon < ActiveRecord::Migration[7.0]
+  def change
+    add_column :grid_weapons, :weapon_key4_id, :string
+  end
+end