Marie-Josèphe Sanson is the younger half-sister of Charles-Henri Sanson and one of the two main characters of the series. Born in 1751 to Charles Jean-Baptiste Sanson and Jeanne-Gabrielle Berger Sanson. Her looks are considered to be too unladylike as she tends to style her sun-blond hair in buzzcut and undercut styles. Usually shaving left side of her head or both sides. She even completely shaved her hair once. Despite her tomboyish appearance Marie is considered as a very beautiful young woman with blonde hair and piercing blue eyes. She has strong physical resemblance to her older brother Charles-Henri Sanson.

Spoiler

Marie becomes a Prévôté de L'hôtel at the age of 11. After witnessing her successful standing decapitation of Marquis Georges de La Tour, the future Duke of Orleans Louis Philippe II takes her to Versailles to act as Prévôté de L'hôtel there.

Spoiler

At the age of 19, Marie engages in a lesbian relationship with the Dauphin of France Marie-Antoinette, after being made her guard by Louis Philippe. After Madame du Barry shares her concerns of Marie's influence on Antoinette with Charles-Henri, he challenges Marie to a duel. Charles-Henri promises to grant her freedom if she wins and to marry her off to the man Charles and his father have approved if she loses. Marie puts all her strength in the duel, and attempts unsuccessfully to kill Charles-Henri. However, Marie is shot in the shoulder with a gun her brother snuck into the duel. Incapacitated and with Charles-Henri's sword at her heart, Marie agrees to marry, with the condition that she could wait until her hair had grown out before the ceremony was held. Just prior the wedding, Marie returns to Versailles, disguised as a proper lady, and attempts to persuade Antoinette to continue her vow not to speak with Madame du Barry, as well as the relationship the two had. However, Antoinette chooses to embrace “adulthood” and finally speaks to the king’s mistress. The wedding is held, but Marie’s betrothed, a distant Sanson named Gaspard, does not show up. Marie begs Charles-Henri to allow to her to instead marry the nephew of Nicolas Sanson, Jean-Louis, a man she claims to love. Both Andre and Nicolas Sanson persuade Charles-Henri further, and he agrees to sign the marriage certificate. A complex plot is revealed once the marriage is official. Jean-Louis Sanson was easily swayed with gifts of food, and Marie convinced him to reinstate her position as Prévôté de L'hôtel if they married. Through the help of one of Marie’s admirers, Chevalier d’Eon, Gaspard was held captive for the duration of the wedding so Marie’s plan could work. Now as a married woman, Marie tells Charles-Henri she is no longer subordinate to her brother’s decisions as Sanson family patriarch, and returns to her position as Prévôté de L'hôtel.

(Source: Innocent Wiki)