As she approaches her graduation next year, her boyfriend Yuta has even kissed her, but nothing beyond that has happened yet. We had promised that we would have a physical relationship only when we were adults. When Rimu comes to her boyfriend's house to play, she meets Yuuta's father Toru, who treats him as kindly as if he were his own daughter. That day, the train stops and Rimu is unable to return home, so she suddenly has to stay overnight. The next day, while Yuuta is away, Tooru gives Rimu an aphrodisiac.