Hiei was born in Koorime, a country of ice Koorimes that floats above Makai. Hiei's mother, Hina bore the child of a fire youkai. This Child was Hiei. Because only ice koorimes are allowed to live in Koorime, Hiei was given the title "Forbidden Child", and thrown off the island as an infant by Rui, Hina's best friend. Rui told Hiei, before she threw him off Koorime, that if he must, he should come back and take revenge on the Koorimes, and she gave him a tear gem his mother had cried. He had one in his possession, and the other was given to Yukina, Hiei's sister. After he was thrown off Koorime, a band of thieves found him. They taught him skills such as thievery and how to fight. he grew so powerful he was abandoned by his new "family" for the fear of their lives. At the age of five, Hiei was a class A youkai. He perused his training with Yukina as his motivation. Hiei learned that Yukina left Koorime to search for him, he went searching for her aswell as his tear necklace that he lost in a fight causing it to fall into a rushing river. Hiei couldn't find either of the two, so to make his search easier, he went to visit a demon known as Shigure. He asks Shigure for a Jagan Eye, and tells his story to him. Shigure gave him the operation, as long as Hiei swore to never tell Yukina his identity. The operation caused his power to sink extremely low. Hiei trained, using the Jagan to build his strength back, slowly raising his strength beyond what it used to be. He learned many new techniques, such as Dragon of the Darkness Flame, and he became able to transform. The transformation process takes only a minute or less the transformation turns his skin green, and eyes appear over his body. Hiei once returned to Koorime, only to find Rui at Hina's grave. Rui asks Hiei to kill her, because Hina comitted suicide over the loss of her son. Hiei didn't answer her, then he disappeared.