"I'm so sorry for suddenly showing you such an embarrassing sight... And to think that I had sex with my son and even felt pleasure from it... I'm a failure as a mother... No... I'm a failure as a human being... I'm partly to blame for this happening..." After her husband's third death anniversary, Rie moved in with her son and daughter-in-law. Rie, who handles the housework, has built a good relationship with her working son and daughter-in-law, and they live together harmoniously. However, the loneliness of her husband's absence leaves Rie physically restless, and she tries to distract herself with masturbation, which has become a daily routine. Late that night, she was satisfying her aching body when her son peeked in. Just as she reached orgasm, her son appeared and forced his hot, erect penis into her body despite her resistance. Having given in against her will, Rie continued to have sex with her son as he desired, but gradually, Rie began to desire him herself. Then, something strange happened to Rie's body. She went through menopause. Feeling that she was finished as a woman, Rie told her son about it and suggested they end their relationship... "My period stopped, and that's when we got even more deeply entangled in this forbidden swamp..."