Aika remarried Kazuhiko, who has a child from a previous marriage, and became the stepmother of Naoya, the only son of marriageable age. Naoya is Kokoro, and no matter how much Aika talks to him, he doesn't open up. One day, Aika sees Naoya being bullied by a classmate, and heads to his room. When she starts talking about the classmate, Naoya becomes enraged and rapes Aika... A secret that should never have happened. However, Naoya tells his bad friend about his relationship with his stepmother, and Aika's hopes of happiness are in vain, even to her son's friends...