Hiei was born in the land of the koorime. At birth, he was cast into the icy cold waters because of his fire energy and because he was sired by a male. Koorime are not allowed to mate, and they can reproduce alone. Hiei was brought up by a band of thieves and was soon cast out, because everybody feared his A-class youki. He later met Kurama in Ningenkai, and afterwards, stole the Shadow Sword from Reikai. As punishment, he had to work as a Reikai Tantei for several months. He has a Jagan Eye and can call out makai flames and ningen flames. At the end of the series, he served Mukuro, formerly one of the three kings of Makai. Hiei also has a twin sister called Yukina.