Mother Mayumi is treated like a mere tool by her husband. Deep down, an illicit bond has begun to form between her and her son, who genuinely cares for her. When her son announces his engagement, Mayumi, overwhelmed by loneliness, finds herself repeatedly masturbating while clutching his underwear. On the day he leaves home to live with his fiancée, Mayumi can no longer suppress her pent-up emotions—and she finally takes action.