Patalliro! The Movie.

Patalliro du Malyner VIII is the crown prince of Malynera, a kingdom that produces diamonds. Despite being ugly and mischievous, he is loyal and fair. Many enemies of the throne, including Malynera's Prime Minister, plan to get rid of him and take control of the rich nation. Patalliro, however, has the protection of Jack Barbarosa Bancoran, his haughty and extremely handsome bodyguard, who will protect him even from the latter's own lover, the beautiful bishonen hitman Maraich Juschenfe and other assassins.