Charles Châtenay is a French artist who draws intimate paintings in the heart of Saint Denis.
The art critics in Paris claimed that he could not draw nor paint, and they told him to pursue his dreams as far away as possible, which made him leave Paris in favor of Saint Denis. When around Arthur, he often refers to himself as a "whole ass," meaning "asshole".
He's probably inspired by Paul Gauguin, a French post-Impressionist artist known for experimental usage of color and who spent the last 10 years of his life in French Polynesia painting people and landscapes from that region.
Charles is first encountered in Doyle's Tavern where he and Arthur start to talk while sharing a drink. He tells Arthur that he has traveled around the world and painted pictures in various countries. He then gives Arthur one of his sketches before leaving.
The following day, Arthur finds an armed and angry man outside of Charles' residence, seemingly furious at the artist for sleeping with his wife. Arthur intervenes and as a sign of his gratitude, and Charles invites him to see his art exhibition.
There are plenty of people at the exhibition when Arthur enters the room, and all are seemingly well. However, the people eventually realize that the paintings portray some of the people present and that Charles might have painted some of them without their consent. The people are outraged at Charles' actions and within a matter of seconds, a fight breaks out in the gallery. However, Charles makes a quick escape and tells Arthur that he is going to lay low for a few days.
At a later point, Arthur stumbles upon Charles who has disguised himself as a woman and tells him that he is being persecuted by the citizens of Saint Denis. Charles tells him that he plans to leave the city and travel to the South Pacific. He asks Arthur to help him get on the next ship but tells him that some of the locals are looking for him. When they arrive at the docks, the pair encounters a group of men who were waiting for Charles and want to enact their revenge. Charles runs to safety all the while Arthur fights the men. After defeating the attackers, Arthur and Charles part ways with a final goodbye.
A letter from Charles can be collected from the post office. Inside, Charles describes his new home and informs Arthur on what a good friend he was to him. He writes how he is finally free, and can now paint whatever he likes.