Her husband, who had found another woman, never returned. Reiko was trying to fulfill her parental duties by raising her son Ryota on her own. However, behind the scenes, she was lonely and miserable, satisfying herself by masturbating every day. Ryota, Kokoro by Reiko's state, decided to embrace her. If it would ease his mother's loneliness, he didn't mind a forbidden relationship. Reiko, feeling her son's intentions, accepted. Wanting to comfort Reiko. With that single mind, Ryota poured his sperm into her to the limit of his physical strength.