A childhood friend and classmate of Junichi. She is something of a tomboy and works as a waitress at a café.
During her arc, Kaoru feels tired with the unchanging state of her relationship with Junichi as old friends. She tries to figure out how she really feels about him. As her feelings for him begin to grow. She struggles to get Junichi to notice her advances as more than friendly gestures.
She is extremely competitive and is good in athletics. Despite not being a part of a sports club. Kaoru shows her jealousy towards Tsukasa when Junichi complements her for being reliable. This results in Kaoru punching Junichi.