Worried about her daughter who had returned to her parents' home after a fight with her husband, Reiko, the mother, decided to stay over at the couple's house for a while. One day, while Reiko was taking a bath, her stepson accidentally opened the door and entered the bathroom with Reiko, and they saw each other naked, creating an awkward atmosphere. That night, Reiko masturbated as she remembered her stepson, and her stepson, unable to forget his stepmother's voluptuous body, knocked on Reiko's door.