Kokushibo

Kokushibo is tall, muscular, and pale, with long spiky black hair tipped in red and worn in a ponytail. His most striking trait is the three sets of eyes across his face, each gold with red sclera and dark lines spreading from the iris. The central pair carries the engraved characters marking his rank. A flame-like Demon Slayer Mark runs across the left of his forehead and down the right of his neck.

He wears a purple and black hexagon-patterned kimono with dark hakama and carries a katana grown from living flesh, complete with eyes set into the handle and blade. As a human he looked nearly identical to Yoriichi, differing chiefly in his thicker, spikier hair. After being beheaded near the end of his life, he warped into a grotesque horned form covered in tubes, fangs, and scorpion-like appendages.

Kokushibo is quiet, distant, and composed, speaking slowly and rarely in a manner that lends weight to his words. A strict observer of the Kizuki hierarchy, he is humble enough to admit difficulty yet harbors a cold, unforgiving streak beneath his dignified surface. He shows selective respect for strong opponents, even sparing Akaza because he enjoyed the challenge, and he scorned Akaza as weak for choosing death to reclaim his lost humanity.

His life was governed by an obsession with legacy and an envy of his brother Yoriichi, whose effortless genius drove him first to abandon his family for the slayers and later to become a demon. Even centuries on, Yoriichi's immunity to the Mark's curse haunted him. In his final moments he breaks down, admitting that the brother he hated most was the one he had only ever wanted to become, and bitterly questions why he was born at all.

As the highest Kizuki, Kokushibo wields power second only to Muzan, refined across nearly five centuries. He is a master of Total Concentration Breathing, a Marked individual with access to the Transparent World, and the demon holding the greatest concentration of Muzan's blood among the Upper Ranks. He severs Akaza's arm before the demon can react and easily overwhelms the Mist Hashira Muichiro.

His flesh katana can never be permanently destroyed since he regenerates it like any wound, and he can sprout dozens of blades from his body. His regeneration is faster than Akaza's or Doma's, and he even regrew his head after decapitation, a feat managed by almost no other demon. His Moon Breathing, the first breathing style ever used by a demon, produces chaotic crescent blades through his Blood Demon Art, and he developed more than a dozen forms over the centuries. Defeating him required three Marked Hashira, bright red blades, and a slayer wielding a Blood Demon Art, and it cost the lives of Muichiro and Genya.