a fanfiction of y/n being muzans twin sister. story: When muzan turned into a demon, he thought that his 'oh so helpful sister' could accompany him. he turned her into a demon...His first demon. He sent her out on a mission to find the cure to his 'sickness' (not being able to walk under sun). (no other demon knew of y/n ,so no y/n is not familiar with any of the upper or lower moons) slow updates ^^