First-year high school student Serina Koshino discovers a love song scribbled all over her desk. Figuring that an upperclassman is responsible for the act, the slightly disturbed Serina is interested in finding out who did it. Later, she finds the culprit: Asuma Mizukawa, a male student who is one year her senior. Despite Mizukawa's aloof exterior, he goes out of his way to help Serina, leading her to immediately fall in love with him.

Even with her blooming feelings, luck is not on Serina's side, as Mizukawa barely acknowledges her existence. Still, the girl refuses to give up on love and hastily confesses to him, which moves Mizukawa enough to become her boyfriend. They may not know each other well but, with the start of their relationship, Serina might see more endearing sides to Mizukawa.