Rui

Rui had a very tragic past, he had a weak body, and he often go outside. Then, Muzan turned him into a demon. After his parents found out, they told Rui not to go out due to sunlight. But Rui killed someone, then his whole family. After that, he was sitting outside. As his mother was dying, she said sorry to Rui that she gave him a weak body. Then Muzan promoted him to become Lowermoon 5. Rui was obsessed to make a fake family that he forces other demons to join his family, and afraid of losing them.