He is a Vampire of the Crimson Moon. Louis had been born into the De Sade aristocracy alongside the likes of Veronica and Dominique de Sade, however because of certain circumstances Count de Sade sent him to live with his grandfather permanently. While living with his grandfather, Louis would come to meet Noé Archiviste and the two would become close friends.

Spoiler

Early in his life Louis was assessed as a potential Curse-Bearer and later thanks to his grandfather would become consciously aware of his condition, which lead him down a path allowing him to resist Charlatan's attempts to control him. Despite this however, when Noé organized a plan to help Mina escape her imminent execution following her diagnosis as a Curse-Bearer - Louis' fear for Noé and Dominique's safety would allow Charlatan the opportunity he'd been waiting for. Louis would proceed to save Noé and Dominique by killing Mina, only to go rogue himself and kill Fanny and Gilles as well. In the end, Louis was killed by his own grandfather when Noé was unable to do so himself by Louis' request.