School beauty Iroha Igarashi is falsely accused of shoplifting in a bookshop, and super-nerd bookworm Tsutsui Hikari a.k.a. "Tsuttsun" comes to her defense. When the sociable Iroha suddenly asks Tsuttsun to go steady he suspects it might just be a novel form of bullying, but it marks the beginning of a relationship between two polar opposites.