The phrase "in tune" is reserved for brass bands. Rei Takaoki is a boy who loves brass band music, with a father who is a professional trumpet player. However, contrary to his feelings, his body, which suffers from asthma, prevents his dream of becoming a trumpet player. He gives up on his dream and goes to a high school that does not have a brass band club. There, he meets the newly established brass band club and the free-spirited trumpeter, Mizune Hoshino. She sees through Rei's love for brass band music and invites him to join the club...