Kurei is Recca's older half brother. He was born in 1571 (four years prior to Recca's birth), and is the firstborn son of Flame Master Ōka and his mistress Reina. He was initially recognized as the next leader of the Hokage clan due to his innate flame powers, but the Hokage elders label him a cursed child when his younger half-brother, Recca Hanabishi, also exhibits the same powers. Kurei was supposed to be killed in order to save the clan, but due to Kagerō's intervention, Kurei and his mother are exiled instead. Kurei attempts to kill Recca, and is imprisoned for his crime. He escapes the prison when it is destroyed during Oda Nobunaga's raid on the Hokage village, and he jumps into the time portal Kagerō opened in order to save Recca by sending him into the future.
Kurei is then found and adopted by Tsukino Mori, the wife of one of the series' main antagonists, Kōran Mori. Kōran raises Kurei to become a "machine", telling him that he does not need human emotions and that he should reject them. Upon seeing how much Kurei loved his mother, Kōran has her transferred to a different house and keeps her under house arrest. When Kurei falls in love with Kurenai, Kōran Mori's adopted daughter, Kōran has her killed. This causes Kurei to despise his adoptive father, but since Kōran is holding his mother hostage, he obeys Kōran's orders.
Kurei is the leader of the Uruha, a group of skilled warriors hired to serve Kōran Mori and to assist Kurei in missions that Kōran orders him to undertake.
Like his father and his half-brother, Kurei has the innate power to produce and manipulate fire. The main form of his flame is the Phoenix, and is a different color from Recca's (Kurei's flames are purple in the anime series and a different shade of red in the Flame of Recca video games). Kurei has the ability to absorb souls into his flame, and use them to produce humanoid flames that fight for him and obey his commands. The first time Kurei absorbed a soul into his flame was when he absorbed Kurenai's soul right after Kōran killed her. The second instance was when he absorbed the soul of a loyal member of the Uruha named Jisho (this is not shown in the anime or the video games). His power is not limited to absorbing just one soul at a time, as shown by his absorption of several souls after an opponent slaughters many men in the latter part of the manga.
Kurei is also capable of executing non-flame based techniques such as Wakemi, a technique that allows him to produce multiple, solid duplicates of himself that possess his powers and skills. In the last part of the manga, he uses the Jikuryūri, a technique that allows its user to open a portal in time.