Kaoru is the daughter of Soji Okita. She uses all sorts of weapons including shikigami of the legendary beasts (Genbu, Byakko, Seiryu and Suzaku). Kaoru takes it personally when she's told about her breast size.
It is revealed later in the series that Okita is actually only half human, having a kitsune mother who married Soji Okita and later abandoned her daughter, claiming she couldn't live among humans. She also has a kitsune older brother. Additionally, she develops a major crush on Ryuunosuke.

(Source: Wikipedia)