Muzan is the first ever demon created centuries ago when he was sick and supposed to die at the age of twenty, he has lived many centuries in search of the blue spider lily to conquer the sun and rule the world, he is in charge of all demons and he eats and devours humans, Muzan is also afraid of a man called Yorrichi Tsugikuni, for they have encountered and he almost died even tho he was already powerful.