Muzan Kibutsuji, a "man" you never want to cross paths with. Not only is he the 1st demon, he is the ruler of all, ruler of the 12 Kizuki. Being a demon or demon slayer is difficult by itself, the 12 Kizuki making it even harder. Implementing fear wherever they go, they have a reign of terror anywhere they step foot. Where they are is somewhere you do not want to be. No one is 100% safe around them, tread carefully, after-all, your mercy is in their hands.