Kumiko Oumae — Sound! Euphonium

In her first year at Kitauji, Kumiko’s struggle with a difficult assigned passage helps turn a casual relationship with the euphonium into a personal commitment. Her desperate wish to improve contrasts with her earlier reluctance to stand out. Reina’s seriousness becomes less intimidating as Kumiko discovers that she, too, wants to care deeply about the result of a performance.

During her second season at Kitauji, Kumiko becomes entangled in Asuka Tanaka’s possible departure from the band. She connects Asuka’s attempt to give up a deeply wanted opportunity with her sister Mamiko’s conflict at home. Rather than accepting Asuka’s self-protective resignation, Kumiko confronts what it means to admit that playing still matters. This parallel sharpens her understanding of how family pressure and unspoken desires can shape a person’s decisions.

Kumiko's second year requires her to support younger players while navigating an increasingly competitive ensemble. By the Ensemble Contest period she has become band president, charged with leading more than sixty members. In her final year the ensemble exceeds ninety; Shuichi serves as vice president and Reina as drum major. Kumiko must now make decisions on behalf of the entire band rather than merely helping individual juniors.

Kumiko's connection with childhood friend Shuichi Tsukamoto is not limited to rehearsals: the two date for a time, although the third-year anime character profile describes that relationship in the past tense. Kanade Hisaishi, a younger euphonium player, develops a particular attachment to Kumiko and remains firmly on her side as disagreements sharpen in the band's final year. These relationships complicate her position as a bandmate and leader without determining how an audition should be judged.

In Kumiko's third year, Mayu Kuroe transfers from Seira Girls' High School, a strong concert-band school, and joins Kitauji with her silver euphonium. Mayu's skill, and her repeated unease about displacing an established member, strain their relationship. Competition auditions force Kumiko to hold two incompatible wishes at once: as president she defends choosing players by ability, but as a musician she longs to perform the featured passage alongside Reina at nationals.

In the anime continuity, the final audition for the featured euphonium passage ends with Mayu selected rather than Kumiko. The players' identities are concealed during the decisive vote; Reina chooses the performance she believes is better, even though she personally wishes to play alongside Kumiko. Kumiko accepts the outcome rather than abandoning Kitauji's merit-based standard. The disappointment is real, but the band goes on to win its long-sought national gold.

Ayano Takeda's original novels resolve the audition differently: Kumiko wins the featured euphonium part in the soli with Reina. The 2026 Final Movement films rework and expand the third television season, including Kumiko's conversations with Mayu and additional performance material. Accounts of the released second film describe Mayu retaining the decisive part; the novel and anime outcomes therefore belong to separate continuities.

Kumiko ultimately decides to become a teacher. The anime's epilogue shows her returning to Kitauji High School as a teacher and assistant adviser to the concert band. The girl who entered high school wanting a reset now helps a new generation pursue the music she nearly walked away from. Director Tatsuya Ishihara also discussed how the original novels conceal the identity of the teacher until their closing reveal.