Kaoru is Kouta's older sister. The first time she meets Kako there is a big misunderstanding. She is a quick-tempered, violent sister who likes to (and often does) boss Kouta around. She likes Kako, so she shares stories and photos about Kouta's past, enjoying reliving every moment of embarrassment Kouta's had. She also cares greatly for Kouta and asks Kako to look after him.