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 also the leader of the Twelve Kizuki, an organization of the twelve strongest demons in existence that serve directly under him.

a millennium ago, during the Heian Era, Muzan was turned into a demon during an experimental treatment by his doctor, who attempted to cure his terminal illness. Making him a vampire who makes demons/aka his minions because he believes they are humans but surperior.

Muzan is a tall and muscular man, with an unnaturally pale skin complexion that can be easily confused as being unhealthy and sickly. He has curly black hair, and sharp, almond-shaped eyes. His irises are cat-like in appearance and colored plum red. He also possesses sharp, blue nails on his hands. He appears to be in his twenties.