On is in his third year of high school. His friends Tsubasa, Masami, Jun and him have always gotten along and the four of them have spent most of their youth in fun together.

On planned to continue his studies in a Tokyo university and though all four of them had chosen to do different things after graduating, he believed that their relationship would still remain the same. However, on the night before their graduation ceremony, when he sneaked into their school with Tsubasa, he was suddenly kissed by the latter!?