Kokushibo is the highest-ranking and most powerful of the Twelve Kizuki, serving directly under Muzan Kibutsuji. Once a legendary Demon Slayer from the Golden Age of the Sengoku Era, he abandoned his humanity to pursue absolute strength and master the devastating Moon Breathing style. He possesses a striking, intimidating presence, defined by long spiky black hair tied into a high ponytail and six piercing, amber eyes marked with his rank. Stoic, intensely disciplined, and cold, he carries himself with the quiet dignity of an ancient samurai. He respects true martial skill but shows absolute, unforgiving mercy to any Slayer who dares cross his path.