Otoha Biwakouji is a seventeen-year-old Japanese high school student and musician in the animated film Kimi no Koe o Todoketai, and one of the seven girls at the center of the story. She studies at Shonan Music Academy, a music school, and is a singer-songwriter; when her friend Ayame Nakahara introduces her to the audience during one of the radio broadcasts, she describes Otoha as a genius singer-songwriter who is still in high school. Otoha has blonde hair and red eyes.

Otoha comes into the story through her friendship with Ayame, who brings her to the group of girls that has revived the abandoned cafe and mini FM station called Aquamarine. From that point, her role in the story is that of the group's musician. She composes and produces jingles and several original songs for the radio broadcasts and is seen playing keyboard as part of that work, so the station's sound is shaped in large part by her music. Her involvement in the group is based on this musical contribution rather than on the personal conflicts that arise among some of the other girls, and she does not drive the group's arguments or decisions.

As the story reaches its turning point, Otoha remains close to the group. When the friends learn that the Aquamarine building is going to be demolished and the station may disappear, she is among those who hurry to the scene, and she takes part in the effort connected with the final broadcast. In the novelization based on the film, her later path continues in music: she moves into the music world and is mentioned as giving live performances, a development that extends the musical ability she shows during the film.