Natsumi is a housewife living with her husband and their college-student son. Though her daily life lacked major hardships, she found herself stuck in a monotonous routine. Her sex life with her husband had long since dried up, and her only pleasure came from masturbating alone at home in the afternoon. But one day, her son accidentally caught her in the act. Tormented by desire, he later became entranced by his mother's body as she prepared to bathe. Overcome with lust, he lost control and finally took her. From that moment on, a new, forbidden relationship began between mother and son.