Louis de Sade was a Vampire of the Crimson Moon in Jun Mochizuki's The Case Study of Vanitas. Louis had been born into the De Sade aristocracy alongside the likes of Veronica and Dominique de Sade, however he was assessed early on as a potential Curse-Bearer; thus Count de Sade sent him to live with The Teacher permanently. While living with his grandfather, Louis would come to meet Noé Archiviste and the two would become close friends. Louis was a tall, thin boy, though, having died in adolescence, still androgynous in build. Like his sister Dominique, he had a small chin, thin eyebrows, upturned, yellow-gold eyes with long eyelashes, and pale skin. His hair was black and straight, falling flat onto his face and cut around to be the length of his face. He had long bangs, parted at the middle, which fell into his eyes. Louis was snarky, skeptical, blunt, and at times outright cruel. He lacked sensitivity towards others, sometimes to the point of hurting their feelings. While he seemed distressed by others' suffering, he was reluctant to apologize or admit wrongdoing. This aloofness seemed to extend even towards himself, and he projected a cold image regarding his supposed status as a cursebearer and thus, his impending demise.