In the cold season, the son cannot suppress his desire to touch his mother's erotic body. In the kotatsu, her wet pussy is played with by fingers until she can't take it anymore and starts breathing heavily. The son's obscene prank that started in the kotatsu escalates... until the stepmother ends up craving the son's dick. The two, transformed into male and female, surrender to their lust and end up committing a forbidden act.
