High school student Totsuko Higurashi, a student at a Catholic school, sees people in terms of colors. She is captivated by the beautiful blue color of her classmate Kimi, and when Kimi suddenly drops out of school, Totsuko sets out to find her. After finding Kimi in a bookstore, Totsuko starts a conversation with her about music, and to the customer who overhears them by chance, she suddenly declares, much to her own surprise, that she wouldn’t mind taking another member into her music group. So, the three guys start becoming friends and decide to compose music themselves.