Muzan Kibutsuji is the Demon King, the first of his kind and the progenitor of all other demons in existence. A millennium ago during the Heian Era, Muzan was turned into a demon during an experimental treatment trying to cure his terminal illness, and his goal since then was to live without the fear of death and become eternal. He's cold-hearted, ruthless, intimidating, and intelligent. He sees no value in humans he encountered and shows little to no value in his own subordinates.