First seen as a lovely dressed young woman who is prettier than Chizuru, Kaoru is actually Chizuru's twin brother who was separated from her during childhood. He's made to dress as a woman but is seen as a boy near the end of the first season of the anime. He is one of the strongest Oni. He wants to make Chizuru suffer because when they were separated, he was taken in by the Nagumo family who treated him harshly for not being a female. He also hates that Chizuru forgot about him and about her even having a twin brother at all. Because of this, he wants Chizuru to feel the pain he felt.