One day, Nagase Junichi, finds a girl being picked on by a bunch of guys. He tries to help her but they run away, declaring him a "Genokiller". The girl asks Junichi for his name, but he decides to act cool, and silently left. Junichi later regrets that he did not introduce himself to her. After the summer break, however, he is surprised when the girl he saved, Katagiri Yuki, abruptly transfers into his class. After a dramatic reunion, a carefree school life starts for Junichi, but all that quickly changes...