Chihaya Katagiri has always been the first trumpet in her school's brass band – until Hibiki Aikawa transfers from a prestigious school and takes the spot. Despite initial suspicions, the two quickly become close; Katagiri admires Aikawa's talent and enthusiasm for playing the trumpet, and Aikawa is struck by Katagiri's grounded treatment of her abilities, as well as her love for music. As their feelings for each other grow stronger, their lives become more complicated with the stress of classes, other relationships, and the last competition of their high school careers drawing near.
