Kazuko Oba, who married for money, appeared to be building a warm family life with her husband and stepson. But one day, the son accidentally discovered her masturbating during the day and secretly meeting with a male insurance agent. Shocked to learn his mother's true motive for marriage was to inherit his aging father's fortune, the son secretly installed hidden cameras throughout the house. He began covertly recording her every move and used the footage to blackmail and coerce her into submission.