Mukuro is one of the Three Kings of Makai. Born into slavery as a sex slave, she endured unimaginable torment from an early age. On her seventh birthday, she chose to pour acid on her body in a desperate attempt to be discarded by her master. After gaining her freedom, she replaced the damaged right side of her body with mechanical parts and wore a mask to conceal her femininity.
Over the following centuries, Mukuro grew stronger, channeling her hatred and trauma into power. She gradually built her own kingdom, eventually becoming powerful enough to challenge the Makai Lord Raizen and initiate a war against him. Her life took a turn when she found Hiei's lost Hirui stone, which had the power to soothe her tormented soul. This discovery saved her from being consumed by hatred.
Mukuro later summoned Hiei to be her ally during the Three Kings war, and they formed a deep bond due to their shared experiences of profound hate and traumatic childhoods. In the anime's Makai tournament, Mukuro fought Hiei and emerged victorious, but he symbolically freed her from her past by breaking the heavy chains that bound her wrists since her days of slavery.
In the manga, Hiei similarly liberated her by capturing her abusive former master and removing a mental block that had prevented her from seeking revenge. Through these acts, both in the anime and manga, Mukuro was able to find some measure of peace and closure.
