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.

Following their success in the qualifying round for the Kansai regional competition, the members of the Kitauji High School concert band set their sights on the next upcoming performance. Utilizing their summer break to the utmost, the band participates in a camp where they are instructed by their band advisor Noboru Taki and his friends who make their living as professional musicians. Kumiko Oumae and her friends remain determined to attain gold at the Kansai competition, but trouble arises when a student who once quit the band shows interest in rejoining and sparks unpleasant memories for the second-year members. Kumiko also learns about her teacher's surprising past and the motivation behind his desire to lead the band to victory. Reaching nationals will require hard work, and the adamant conviction in each student's commitment to the band will be put to the test.

Kumiko is now a second year and one of the senior players of the euphonium section. With new underclassmen joining the concert band, Kumiko will have to learn new things in order to deal with awkward and difficult underclassmen. She and third-year trumpeter Tomoe Kabe have been chosen to lead the new underclassmen members. Among the new members to Kumiko's bass section are euphonist Kanade Hisaishi, whose appearances are deceiving; tuba player Mirei Suzuki, who cannot adapt to her new environment; tuba player Satsuki Suzuki, who wants to get along with Mirei; and double bassist Motomu Tsukinaga, who cannot talk about himself. Between the Sunrise Festival, chair placement auditions, and the competition, a number of problems quickly begin to arise.

Awaiting new club leader Kumiko is the Ensemble Contest -- a.k.a. "EnCon"-- and the school's preliminary competition to determine the representative team to participate. Kumiko tries her best to make it to the preliminaries without incident, but the concert band club is so large that there seems to be no end to the problems... And as the club leader, she finds herself busy consulting on all sorts of matters. While the club members are deciding on their teams, Kumiko herself hasn't even decided which she will join...

In their last year of high school, two girls in the brass band club perform a song inspired by a fairy tale that parallels their friendship.