Lupin the 3rd

The Black Lilly Party, obsessed with restoring the aristocracy, tries to get Lupin to find the phantom Crown of Marie Antoinette. On a hint from Oscar, the young, very attractive leader of the Black Lilly's Stormtroopers, Lupin removes the crown from a hidden compartment in a mirror at the palace of Versailles, but, breaking the promise of a 50/50 split, Oscar takes the crown and turns fugitive. What is Oscar's true identity?