Haruka Morishima's best friend and captain of the girl's swim team. She is often seen with Haruka.
Hibiki is a calm student who seemingly has no problems with school or personal life. She spends a lot of time with Haruka, whether it is in school or otherwise. Hibiki acts sort of like a quiet and patient older sister to Haruka. As the captain of the school's girl's swim team, she expects all the girls to do their best.