Muzan Kibutsuji (鬼き舞ぶ辻つじ 無む惨ざん Kibutsuji Muzan) is the main antagonist of Demon Slayer: Kimetsu no Yaiba. He is the Demon King, the first of his kind, and the progenitor of all other demons in existence. Muzan is the leader of the Twelve Kizuki, a group of the twelve strongest demons in existence that serve under him. A millennium ago, in Heian Era, Muzan was turned into a demon during an experimental treatment trying to cure his terminal illness, he's been searching for the Blue Spider Lily.