Kokushibo

Kokushibo is Upper Moon One of the Twelve Kizuki in Demon Slayer, serving as the strongest demon under Muzan Kibutsuji. Kokushibo was formerly known as Michikatsu Tsugikuni, the older twin brother of Yoriichi Tsugikuni. Kokushibo possesses extraordinary sword skills as a former Demon Slayer turned demon. Kokushibo harbors deep-seated jealousy towards Yoriichi's natural talents. Kokushibo maintains an elegant and composed demeanor even in battle. Kokushibo demonstrates immense pride in swordsmanship and martial prowess. Kokushibo shows particular interest in strong swordsmen, especially those who remind Kokushibo of Yoriichi. Kokushibo's relationship with moon breathing techniques has shaped Kokushibo's combat style significantly. Kokushibo's transformation into a demon was driven by the fear of death and desire for strength.