Mother Leona is called in by the school after her son Seiji submits a blank answer sheet for his health and physical education exam. During the meeting, Leona realizes that Seiji still lacks sexual interest and knowledge. Later, Kazuki, a classmate of Seiji's, suggests that Leona and himself demonstrate sex in front of Seiji to educate him. Hesitant at first, Leona ultimately gives in to Kazuki's pressure, fearing that Seiji will become a target of bullying, and decides to perform sex in front of her own son.