Luis Riston is a supporting character in the anime With Vengeance, Sincerely, Your Broken Saintess. He is a boy who comes from a small country in the east and serves as the exclusive personal servant of Diana Peridot at the Duke Peridot manor. His personality is defined by honesty and kindness, making him a gentle and reliable presence in the household. In the story, his primary role is that of a loyal attendant to Diana, though he also maintains a connection with the protagonist, Rua Restoatt, the nature of which is hinted at but not deeply explored in available material. His background as a foreigner and his sincere demeanor set him apart from the more politically motivated characters around him. No special combat or healing abilities are attributed to him; his function revolves around service and support. Character development for Luis Riston appears limited in the early arcs, and his motivations center on faithfully carrying out his duties to Diana while navigating the tensions within the court.