Shy first-year high school student Minato Asano has managed to keep to her resolve of avoiding unnecessary interactions with others. But this resolve becomes all for naught the moment she hears a random melody within the grounds of a school not known for having a music club; the source of the sound is the bubbly second-year Hibiki Sugawa, who has actively sought out Minato to get the easily-flustered girl to join her new concert club.

Finding that the drummer will not take no for an answer, Minato is persuaded to bring her trombone and meet the other band members: bass guitarist Chika Inagaki; flutist Sakiko Arita; and Ema Nonaka, who occasionally drops by with her skills on the saxophone, guitar, and piano. Though wary of the group at first, Minato slowly finds herself opening up to people once more as she casually jams with Hibiki and the other members.