A man and woman, now step-siblings due to their parents' remarriage, find themselves alone together for the first time at home. Sitting together under the kotatsu in the living room, they gradually become aware of each other's presence. Though they know the close contact under the kotatsu is dangerous, their excitement grows uncontrollable. The woman slowly becomes wet while the man, erect and throbbing, struggles to hold back. Unable to resist any longer, they give in and have sex right there before their parents return. They indulge in the pleasure of bareback creampie, consumed by the intense intimacy.