Kumiko Oumae has become the new president of the Kitauji High School concert band, navigating her demanding final year with her ex-boyfriend Shuichi Tsukamoto as vice president and her close friend Reina Kousaka as the drum major. Set against the backdrop of a band now determined to win the national championship, the story follows the ensemble as they welcome a new group of first-year students, including the talented and ambitious euphonium player Mayu Kuroe, a transfer student from the prestigious Seira Girls School. The narrative arc focuses on the mounting tension and emotional conflict between Kumiko and Mayu, who plays the same instrument, as they compete for the euphonium solo position crucial to the band's competition performance. As the band intensifies its rehearsals, the members must confront their personal doubts and interpersonal frictions while striving for musical perfection. Featured scenes include the annual Sunrise Festival marching band event and the rigorous preparations leading to their final stage at the national competition held at the Century Hall in Nagoya, where the graduating seniors face what is likely their last performance together.