belongs_to :speech_balloon
belongs_to :system_picture
- validates :speech_balloon_id, :presence => true, :numericality => true, :existence => true
+# validates :speech_balloon_id, :presence => true, :numericality => true, :existence => true
validates :system_picture_id, :presence => true, :numericality => true, :existence => true
validates :x, :presence => true, :numericality => true
validates :y, :presence => true, :numericality => true