Rui Tsukihiko is a prominent antagonist in the anime and manga series Kimetsu no Yaiba (Demon Slayer). As Lower Rank Five of the Twelve Kizuki, Rui is a powerful demon who controls a family of other demons in Natagumo Mountain. He possesses the Blood Demon Art of manipulating threads, making him a formidable opponent. Rui's obsession with the concept of family and his desire for parental love drive much of his tragic and twisted actions, ultimately leading to a memorable confrontation with Tanjiro and Nezuko.