After quitting her job as a teacher, Miki (Reiko Makihara) left Tokyo, where she had been living, and returned to her family home. She had chosen a forbidden love, severing the mother-son relationship, yet deep inside, she harbored complicated emotions. Meanwhile, Minami boldly claims that "sex is just like a sport," but unable to accept the relationship between Tsuyoshi and Miki, who is much older, she forcefully drags Tsuyoshi into her room, strips naked, and provocatively challenges him. When Miki finds out about Tsuyoshi and Minami having sex, she is shocked, but at the same time begins questioning her own relationship with him. Tormented by doubts over whether she has the right to hold back young Tsuyoshi's future, Miki ultimately resolves that they must not stay together. That night, after passionately making love to Tsuyoshi, she tells him it's time to return to being mother and son.