Natsumi is Hina's childhood friend who she used to play with when she visited her grandfather in the summers. Initially Hina didn't recognize her but she plays a big part in keeping her in the club because she is someone she knows.

Natsumi seems like she is just a tomboy but she isn't, she in actuality is very good student much to Hina's surprise and very supportive of Hina's growth as a fan of fishing.