Kokushibo (Upper Moon One)

Kokushibo is Upper Moon One, the strongest of the Twelve Kizuki in Demon Slayer. He is a calm, stoic, and extremely powerful demon with six eyes. Once a human swordsman named Michikatsu Tsugikuni, he is the older brother of Yoriichi Tsugikuni. He possesses unparalleled swordsmanship and immense strength.