Kumiko Oumae wishes to forget her past now that she has enrolled in Kitauji High School. Despite her wish for a new beginning, she is pulled into the school's band club by her new friends, Sapphire Kawashima and Hazuki Katou, and is once again forced to play the euphonium. As things are, the band will be unable to participate in the local event Sunfest, let alone compete on a national level. Noboru Taki, the band's new adviser, gives them a choice: relax and have fun, or prepare hard and try to make it to nationals. Kumiko is unsure if they should compete at nationals since she does not want to repeat her errors from middle school. In the middle of the pandemonium, she discovers that her old bandmate, Reina, has died.