The protagonist enters wind ensemble club after being asked by her friend. She steps into the world of wind music without much thought, longing to be like her sister who plays the euphonium. Exposed to the powerful emotions of friends and members, her image towards the euphonium gradually shows a change. Friendship and rivalry, selfish hopes and despair, respect and doubt towards seniors, battle between talent and effort, accepting loss, the girls find an irreplaceable something through their serious struggles. Many challenges to animation such as hand-drawn instruments vibrating, and synchronisation between finger movement and sound appear on the film.