Kokushibo is a major supporting antagonist of Demon Slayer: Kimetsu no Yaiba. He is a demon affiliated with the Twelve Kizuki, holding the highest position, Upper Rank One. Kokushibo was a human by the name of Michikatsu Tsugikuni, a former Demon Slayer, and the older twin brother of Yoriichi Tsugikuni. Kokushibo is the ancestor of Muichiro Tokito, And Yuichiro Tokito. Kokushibo had a wife and two children, but left them. Akeno Tsugikuni, his mother. And Uta, his sister in law. (Yoriichi's wife)