Atsushi returns to his parents' home during a break from university. He is shocked to find out that his father has remarried his former teacher, Yumi, a woman he admired... Living under the same roof, Atsushi can no longer contain himself and confesses his feelings to her. At first, Yumi rejects his confession, but when she accidentally sees his powerful cock, her sexless body is Kokoro, and she can no longer resist and accepts it. Her secret relationship with Atsushi, who is both her student and her son, brings out more pleasure in her than any sense of guilt...