Riko Nagase is a second-year student at Kitauji High School, playing tuba in the concert band and one year senior to Kumiko Oumae. Her appearance features dark brown hair styled in twin low buns, brown eyes, and relatively thick dark eyebrows. She is of below-average height with slightly above-average weight and wears the standard second-year Kitauji uniform. Polite, soft-spoken, friendly, and respectful toward everyone, Riko possesses a gentle demeanor that often calms others, though she commands respect through seriousness when needed. She maintains a private romantic relationship with fellow tuba player Takuya Gotou, built on mutual support and encouragement. While she keeps this relationship discreet, it becomes known among peers who occasionally tease her. Her background includes participation in the bass section during the band's efforts to qualify for national competitions. The name Riko means "pear child," and Nagase means "long swift current" or "chief rapids."