Aya, who has come to Tokyo on a school trip, uses her free time to go and visit her brother, Jun, who she was separated from after her parents' divorce. Although Aya has a boyfriend named Nobu, she can't help but think about her brother. Aya had harbored a secret crush on her brother since childhood and wanted to confirm her feelings upon their reunion. Meanwhile, Aya's boyfriend was not pleased. As a virgin, Nobu had planned to have sex with her for the first time during the school trip, but Aya went to see her brother instead. On the second day, Nobu secretly followed her. He then witnessed Aya and Jun in a passionate embrace in Jun's room…