Birthdate: December 25, 1755

Born the last of five daughters to the Commander of the Royal Guards, General François Augustin Regnier de Jarjayes she is raised by her father as if she were a boy in order to take his place and command the Royal Guards serving at Court after he retires. At the age of fourteen, as soon as her training in the basic military skills is complete, Oscar is given the task to protect the Dauphine Marie Antoinette when she arrives at the French Court.

Despite being raised as if she were a boy and dressing in males' clothes, Oscar is open about being female. Even as she embraces her femininity, she uses her male position to gain freedoms that she could never have as a lady of the court.

She is the love interest of both André Grandier, her servant at the Jarjayes mansion and afterwards a soldier in her regiment, and Marie Antoinette, who she acts as a bodyguard to. She also earns the admiration and love of Rosalie Lamorlière, and in turn calls Rosalie her "spring breeze". Other women are infatuated with Oscar, even after she tells them she is female. She dislikes the court intrigues, but remains there out of loyalty to her father and her friend, Marie Antoinette. At one point, Oscar falls in love with Fersen, who has a forbidden love for Marie Antoinette.