Kokushibo (黒 (こく) 死 (し) 牟 (ぼう) , Kokushibō?) 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 (上 (じょう) 弦 (げん) の壱 (いち) , Jōgen no Ichi?).[2] Nearly five centuries ago during the Sengoku Era, Kokushibo was a human by the name of Michikatsu Tsugikuni (継 (つぎ) 国 (くに) 巌 (みち) 勝 (かつ) , Tsugikuni Michikatsu?),[3] a former Demon Slayer,[4] and the older twin brother of Yoriichi…