On Kyouya Sata's 17th birthday, his girlfriend Erika Shinohara seems to have forgotten about the occasion. Even her best friend Ayumi Sanda doesn't realize when she asks Kyouya to tutor her after school. However, Erika is secretly planning a birthday surprise for Kyouya at his house and enlists Ayumi to distract him. But things go wrong and accidents happen, making Erika anxious and Kyouya has to calm her down as his unusual girlfriend gets worked up.