Rui is a prominent antagonist from the anime series 'Kimetsu no Yaiba' (Demon Slayer). He is one of the Twelve Kizuki, holding the position of Lower Rank Five under Muzan Kibutsuji. Rui is notable for his spider-themed abilities and his desire to create a 'family' of demons to fill his loneliness. Despite his youthful appearance, Rui is sadistic and powerful, posing a significant threat to the protagonists. His tragic backstory adds depth to his otherwise menacing role.