Muzan Kibutsuji was the Demon King and the primary antagonist of Demon Slayer: Kimetsu no Yaiba up to the series’ finale, who remained almost invincible during the whole show. Since the introduction of the character, he has been depicted as a being that possesses invincibility, a character who had been training for centuries and getting rid of all that posed a threat to his existence. However, he was cornered during the final fight and unveiled his final form, which was the final addition to his arsenal.