Kibutsuji Muzan can be killed by exposing him to sunlight, which will burn his cells and prevent him from regenerating. However, this is easier said than done, as Muzan can hide his presence and disguise himself as anyone. He can also fight back with his overwhelming power and cunning. Another way to kill Muzan is to use a special sword called the Nichirin Blade, which is forged from a special ore that absorbs sunlight. The blade can cut through a demon’s flesh and prevent it from healing. However, to kill Muzan, the blade has to be coated with a special poison that slows down his regeneration, and the user has to strike his 12 vital organs in a specific order within a short time span.