After swearing off music due to an incident at the middle school regional brass band competition, euphonist Kumiko Oumae enters high school hoping for a fresh start. As fate would have it, she ends up being surrounded by people with an interest in the high school brass band. Kumiko finds the motivation she needs to make music once more with the help of her bandmates, some of whom are new like novice tubist Hazuki Katou; veteran contrabassist Sapphire Kawashima; and band vice president and fellow euphonist Asuka Tanaka. Others are old friends, like Kumiko's childhood friend and hornist-turned-trombonist Shuuichi Tsukamoto, and trumpeter and bandmate from middle school, Reina Kousaka.

However, in the band itself, chaos reigns supreme. Despite their intention to qualify for the national band competition, as they currently are, just competing in the local festival will be a challenge—unless the new band advisor Noboru Taki does something about it.

Misaki decides to join the Brass Band Club having heard of its prestigious past from her father, a former member. However, Misaki finds that much has changed and the club is now full of dull and inactive students. Misaki determines to do her best to return the club to its glory days, but she must help many of the students overcome their personal problems.