In the midst of a painful and unfulfilling married sex life, Yū, the wife, is slowly breaking down emotionally due to her husband Yoshihiro's infidelity. Blaming herself, she grows increasingly exhausted by daily life. Enter her kind-sounding father-in-law, Junji, who pretends to comfort and encourage her. Under the guise of helping, he tells her, "Your marriage fell apart because your sex life wasn't working," and begins teaching her the ways of sex. Though innocent and pure, Yū knows deep down she's doing something wrong—but she also realizes she secretly desires something more. Holding onto that forbidden longing, she chooses to surrender herself completely.