Kurogin Academy has decided to become co-ed, but it starts when the seniors have already graduated. Tsuchiya, a student of Yankumi's, was in a bookstore when he catches a junior high female student attempting to shoplift. Tsuchiya can't leave the girl alone, so he introduces the other side of studying and brought her to an arcade, where she starts to have fun. However, a former homeroom teacher of Tsuchiya catches him and the teacher automatically blames and accuses Tsuchiya of forcing the girl to hang out with him. The situation starts to heat up as Yankumi realizes that Tsuchiya can potentially be expelled from Kurogin Academy.
