Rui was a member of the Twelve Demon Moons, having held the position of Lower Moon Five. Rui has the appearance of a young boy. His skin is white, with red dots. His hair is light pink and bears resemblance to spider legs. The sclera of his eyes are red, while his irises are pale blue. His blood demon technique allows him to create strings that are hard to cut. He is able to use the strings in both offensive and defensive way, by either using them to cut something or to block attacks. (Source: Kimetsu no Yaiba Wiki)