Kaoru is always gentle and kind, living peacefully with her son Takuya. After losing her husband, she built a warm home with him. However, she had been satisfying her desires alone through masturbation—until one day, when her son's friend visits, awakening long-suppressed urges. During Takuya's absence, his friend Takeshi comes over. Wearing seductive lingerie, Kaoru tempts him, and a secret, passionate relationship begins between them.