Rainbow Days centers on a group of four male high school students who are close friends: Natsuki, Tomoya, Keiichi, and Tsuyoshi. The four boys have no club activities, and they hurry through their studies so they can spend their days having fun. Their main topic of interest: love. Natsuki has an unrequited crush on Anna, a girl from another class, and his friends keep meddling in their relationship.