Kokushibo

Kokushibo, known as Michikatsu Tsugikuni, was the Upper Rank One demon. Driven by intense jealousy toward his brother, Yoriichi, he sacrificed his humanity to become a demon in pursuit of strength and immortality. He mastered Moon Breathing, a unique style that mimics his blood demon art. As a swordsman, his skill was unparalleled, making him the most formidable antagonist among Muzan's Twelve Kizuki.