Ribbon no Kishi (1999)

Princess Sapphire was born with both a boy's heart and a girl's heart after a mistake in heaven. Because only a male heir may inherit Silverland's throne, she is raised publicly as a prince, carrying a secret that could cost her family the kingdom if it is exposed.

Duke Duralumin and those around him seek to uncover Sapphire's true identity and remove her from the succession. Yet even as political schemes close in and her own wishes pull her toward a different life, Sapphire refuses to surrender the future of her people, holding on to the hope that she can choose her own path despite the role forced upon her.