One year after separating from her husband, Emiko (RYU) lives alone with her son, Ryusuke. One night, Ryusuke accidentally sees his mother masturbating in her room, and he begins to develop abnormal feelings toward her. Exposed to his mother's unexpectedly seductive side, Ryusuke becomes overwhelmed with uncontrollable excitement. Unable to hold it in, he confesses his desires and pleads for intimacy. Though initially hesitant, his mother rationalizes it as "sex education" and agrees, beginning to teach him about sex using her own body. How will this new relationship between mother and son continue to evolve?