A character from Sound! Euphonium. Full name: Natsuki Nakagawa. Height: 156cm. Blood type: A. Birthday: June 23rd. Instrument: Euphonium. Zodiac sign: Cancer. Favorite colors: Purple, Black. Hobbies: Guitar, Karaoke. She is incredibly fast at mental arithmetic, though she is poor at formal mathematics. Likes bears and spicy food; dislikes matcha and red bean paste. A member of the bass section playing the euphonium. She is a student with a somewhat lazy atmosphere who usually maintains a cynical, detached attitude, often using a playful, sarcastic smile to dodge showing her true feelings. She was originally a beginner who started band after entering high school. She initially wanted to play the saxophone, but due to the quota being filled, she was assigned the euphonium.

A character from Sound! Euphonium. Full name: Yuko Yoshikawa. Height: 156cm. Blood type: B. Birthday: April 15th. Instrument: Trumpet. Called Yuko by Natsuki, Mizore, and Nozomi. Zodiac sign: Aries. Favorite colors: Yellow, Pink. Hobbies: Guitar, Karaoke. She has never lost at the game of Concentration. Likes croquettes; dislikes soba and static electricity. Possessing a spirited personality, she has significant influence within the club due to her straightforward way of speaking. Furthermore, she is deeply trusted by her fellow members because of her selfless attitude and her honest, pure-hearted nature. Like Nozomi Kasaki of the flute section and Mizore Yoroizuka of the double reed section (oboe), she is an alumna of Minami Middle School, a powerhouse band school. Despite facing many difficulties—such as a bitter experience at a competition in middle school and being troubled by the lack of motivation among seniors when she first started high school club activities—she has continued with the band club without breaking to this day.

A character from Sound! Euphonium. Full name: Mizore Yoroizuka. Height: 154cm. Blood type: AB. Birthday: July 2nd. Instrument: Oboe. Called Mizore by Natsuki, Yuko, and Nozomi. Favorite colors: Blue, Navy, Grey. Hobbies: Lounging around at home with her cat. She is strong at rhythm games and psychological warfare games. Likes carbonated candy and soda; dislikes places with poor reception. She is constantly expressionless and rarely shows emotion; combined with her shy personality, she doesn't have many close friends in the club. She devotes herself to fundamental practice from early morning until late at night every day, and her performance skills—which pursue precision to the extreme—are held in high regard by many members, including Vice President Asuka Tanaka. Having previously played in the band at the elite Minami Middle School, Mizore joined the Kitauji High School band to follow her best friend, Nozomi Kasaki. However, when Nozomi quit the club after a conflict, unable to stand the environment at the time, Mizore was deeply scarred, and her playing—which once possessed rich expressiveness—became cold and devoid of emotion.

A character from Sound! Euphonium. Full name: Nozomi Kasaki. Height: 159cm. Blood type: A. Birthday: December 3rd. Instrument: Flute. Called Nozomi by Natsuki, Mizore, and Yuko. Zodiac sign: Sagittarius. Favorite colors: Purple, Pink. Hobbies: Photography. Her special skill is dancing. Likes natto, okra, and mountain yam; dislikes imitation crab and hanpen. She has a bright, active personality and is full of initiative, always surrounded by close friends. Her playing skills are also excellent, with a tone colored by joy and passion. Like Mizore Yoroizuka and Yuko Yoshikawa, she is from the powerhouse Minami Middle School band, where she served as the president and leader. Although she continued band after entering Kitauji High School, she couldn't stand the lazy atmosphere of the club at the time and quit along with other classmates after a rebellion. However, the following summer, after witnessing the transformation of the club under the guidance of the new advisor Noboru Taki, she was inspired by their unified effort and requested to return to the club after about a year's absence.