Suruga Koteyama is a side character in the Hibike! Euphonium series. She is a first-year student at Kitauji High School who joins the band as a bassoonist in Kumiko Oumae's second year. Additionally, she played the contrabassoon in Liz and the Blue Bird.

The third season of Hibike! Euphonium.
 
Kumiko's third year finally begins! With the concert band at Kitauji High School over 90 members, Kumiko is now the president and does her best with her final high school club activities to try to win her long-desired gold at nationals.
 
(Source: Crunchyroll, edited)

Along with the summer brass band competition, the ensemble contest, commonly known as "Ancon," is a place where exciting performances are held. The performance of several people in one group has a charm different from that of a competition. 

In order to participate in the Kyoto prefectural tournament of Ancon, a representative team is selected in the school's preliminary round. However, with over 50 members, the Kitauji High School brass band is facing a variety of problems! Will Kumiko, the newly appointed head of the club, be able to make it through the preliminary rounds? 
The days of struggle begin. 

(Source: Official Site, translated)

The next piece begins! Kumiko is now in her second year at Kitauji High School, and with a new year comes new problems. As if making it to Nationals wasn't hard enough, Kumiko is tasked with mentoring the concert band's troublesome first years – each with their own distinct personality and problems to solve. With Kumiko busy juggling both the concert band and her new role as senpai, how does her relationship with Shuuichi fit into the picture? 
 
(Source: Shout! Factory)

Students and best friends Mizore Yoroizuka and Nozomi Kasaki prepare to play a complex musical duet, Liz and the Blue Bird, for oboe and flute. Though they play beautifully together and have been friends since childhood, Mizore and Nozomi find that with graduation looming and the duet proving difficult, their friendship begins to buckle under the pressure. Interspersed with their story is the fantasy tale of Liz, drawn like a storybook, contrasting with the crisp realism of the school. 
 
(Source: Shout! Factory)