Muzan Kibutsuji is the primary antagonist of the anime "Demon Slayer" (Kimetsu no Yaiba). He is the first and most powerful demon, responsible for creating all other demons by infusing them with his blood. Muzan seeks to achieve true immortality by overcoming his weaknesses to sunlight and Nichirin blades, driven by a deep fear of death. He is known for his cruel and ruthless nature, treating humans and demons alike as expendable tools to further his goals. Muzan maintains control through fear and manipulation, operating in secrecy while continuously striving to perfect his demonic powers and eliminate the Demon Slayer Corps.