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 progenitor of all other demons in existence, and the leader of the Twelve Kizuki, an organization made up of the twelve strongest demons under his direct command. [5] A millennium ago during the Heian Era, Muzan was turned into a demon from an experimental treatment for his terminal illness[1] and his goal ever since then has been to live without the fear of death and become truly eternal.[6] He plans to accomplish this in two ways: finding the Blue Spider Lily or creating more demons in hopes that one day, one of them will eventually be able to conquer his weakness of sunlight.[7][8] It is later revealed that Muzan is also of the same bloodline as the Ubuyashiki Family.[9]