Marimo Hatanaka is a fourth grader from the Star Class at Seiyo Academy. She appears in Episode 045, auditioning to play the accompaniment on the piano for the Choral Competition Seiyo Academy was entering. She becomes friends with Seiichiro Suzuki and helps him practice singing because he wasn't the best at it. She tells him her dream was to play the piano always, even after she got married and had children; hoping to play with them.