Hiei was born in the Floating Kingdom of the Koorime, high above Makai. The Koorime were a race of ice youkai, legendary snow maidens who had the ability to cry pearls. Tradition had long held that the mothers of the Koorime gave birth to female twins, both ice youkai...
But Hina, Hiei's mother, had loved a fire demon, and as a consequence, she gave birth to Hiei and Yukina - one a male fire youkai, the other a Koorime girl. The boy child was condemned by the Koorime elders as a sign of misfortune, not to mention a grave threat to the Floating Land of the Koorime, being a fire demon. They commanded Ruri, a friend of Hina's, to cast the child over the edge of their lands to die far below in the wilds of Makai. Hina could do nothing but watch as her son was dropped into the fathomless cloaking mists that surrounded their land.
"Let me go with him at least," she had begged the Elder, tears flowing down her face. "Let me at least be the one who raises my son!"
But she had been adamantly refused.
Hina had shed two hiruiseki (tear-gems) during the birth of her twins, one for each child. As Ruri held Hiei, bandaged and warded to keep his powers sealed, over the precipice, before she dropped him she tucked one of the hiruiseki into his wraps, murmuring, "When you grow strong, come back if you will and take your vengeance upon me."
Hiei survived the fall, to be taken in by a band of thieves. Upon growing older he left them to wander Makai alone, and fell into a fight with another youkai, losing his tear-gem in the process. He approached a youkai named Shigure, who gave him his Jagan, the third eye, which could 'see beyond,' sense ki signatures, spirit-auras, and so on, within a mile radius. It also enabled him to exert control over the fires of Makai and the Black Dragon. With it, he thought to obtain the gem, and learn more about his origins, including his sister. But Shigure threatened to kill him if he ever revealed himself to Yukina as her brother, for reasons unknown.
He returned after long years to the realm of the Koorime, only to find it a veritable ghost town. There he found the Koorime woman Ruri, who, realizing it was the Forbidden Child returned, revealed to him that Yukina, his twin sister, had left for Ningenkai to seek him out. She fell to her knees in an agony of terror, thinking she would be killed, but surprisingly, Hiei simply left her, and left to seek out his sister.
It was during his long search that he met Kurama, a thief by profession, and fought him, losing only by accident. When Hiei awoke, his wounds had been already tended to, and to repay Kurama he helped the kitsune kill a certain youkai. Discovering that their fighting techniques meshed well together, they decided to form a partnership, and became best of friends, though Hiei will not willingly admit it.
With Gouki, another demon, they stole the Three Treasures of Reikai, the Sword, the Mirror, and the Gem, each with their respective powers: the Sword could turn any creature it cut into a monster; the Gem could entrap souls; and the Mirror could grant one wish, in exchange for a life. Kurama had wanted the mirror to cure his ailing human mother Shiori, with his life as payment.Yuusuke, sent to stop them as a Reikai Detective, killed Gouki, and helped Kurama by offering half of his life to save Shiori. The Mirror broke, granting Kurama's wish but taking nothing in return.
Hiei fought Yusuke, only to be stopped by Kurama, who took Hiei's blade through the stomach by accident. Hiei was defeated, and taken to Reikai to be held. He and Kurama were given a chance for pardon, but only if they entered Reikai's service as members of the Reikai Tantei. Thus did Hiei become the fourth Spirit Detective.
Hiei Joined Yusuke on many adventures. In one of them they were assigned to rescue Yukina from the clutches of a greedy merchant, Tarukane, who had captured and imprisoned the girl so he could torture her and sell her tear-pearls. It was during this mission that Hiei met his sister again, though he never told her a thing. Kuwabara fell in love with Yukina upon first sight, only increasing Hiei's distaste for the tall clumsy human.
Hiei battled in the Dark Tournament where he unleashed the power of the Black Dragon. He lost conciseness and got amnesia. Now he's come to his senses He's become alot weaker since and his friends' whereabouts are unknown. He now fights and trains so he can become the once Strong and legendary demon he once was.