Muzan Kibutsuji is the main antagonist and the Demon King in Demon Slayer: Kimetsu no Yaiba, the progenitor of all demons, and the leader of the Twelve Kizuki. He was once a human who became a demon a millennium ago in an attempt to cure his terminal illness, but this resulted in his weakness to sunlight. His primary goals are to find the Blue Spider Lily and create a demon immune to sunlight to achieve true immortality and conquer his weakness. 