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.
Episode 1
Kumiko enters Kitauji High School having been unable to forget what Reina said at a middle school concert band competition. She goes to visit the concert band at school along with classmates Hazuki and Sapphire, where they meet Reina again.
Episode 2
Kumiko and the others join the concert band, and they choose their instruments. Their eccentric senior, Asuka, still likes to mess with them.
Episode 3
Kitauji High School Concert Band is preparing their parts for the ensemble, but some students are fooling around when they should be practicing.
Episode 4
Kumiko and the others prepare for Sunrise Festival. Kumiko and Shuichi talk about Taki-sensei on the way home from school, when they run into Reina.
Episode 5
The concert band receives their marching band uniforms and begins marching practice in preperation for SunFes. Things are different now, with the members all more engaged in practice. And SunFes day arrives.
Episode 6
Starting this year, the band holds auditions for members participating in the competition. First-year Hazuki has a chance, too. The bass section does everything they can to encourage her.
Episode 7
The band is hard at work preparing for the audition and the competition. Aoi has trouble with her part, to which Taki says, "when will you be better by?"
Episode 8
The band is abuzz with talk about who they'll be going to the upcoming festival with. There's someone Hazuki wants to go with, but that someone is already going with someone else. Meanwhile Kumiko somehow ends up going with you-know-who.
Episode 9
The audition for the competition participants has come. Everyone must demonstrate their abilities, whether they're a third-year or a first-year. And then, the results are revealed.
Episode 10
The band suspects Taki played favorites in choosing Reina in the auditions. Noticing the band's rising distrust of Taki and Reina, he makes a proposal.
Episode 11
Taki-sensei's proposal relieves the upset within the band, and everyone returns to practicing. Reina no longer isolates herself either, much to Kumiko's relief. But then she sees Yuko, who's been antagonizing Reina, speaking with her.
Episode 12
The competition's coming up. Kumiko is suddenly asked to play a difficult phrase from a different part. She begins practicing, but...
Episode 13
The competition performance is "only" 12 minutes long. It's both a blink of an eye and an eternity. The Concert Band members bet their entire youths on this competition. And Kitauji High School Concert Band's performance begins.
