Prince Franz Charming, heir to the neighboring kingdom of Goldland, is raised by his uncle after his mother’s untimely death, molded to prioritize royal obligations—including a politically advantageous marriage he initially defies. His life intertwines with Sapphire through three guises: as Prince Sapphire, a trusted confidant; an unnamed princess (Sapphire disguised with a blonde wig), whom he grows to love; and the masked Phantom Knight, a perceived romantic rival.

Baron Nylon orchestrates a treacherous duel, arming Franz with a poisoned blade to frame him for assassinating Sapphire’s father. The ensuing arrest fractures their bond and forces Franz to confront his loyalties. To spare Sapphire’s life, he reluctantly pledges marriage to Hecate, daughter of the witch Madame Hell, a decision that costs him his uncle’s favor and his royal status.

Over time, Franz navigates the tension between duty and desire, defying societal norms to shield Sapphire and oppose corrupt powers like Duke Duralumin. His evolution culminates in aiding her defense of Silverland, confronting threats like the proto-fascist ruler Mr. X through strategic alliances and battlefield prowess.

Adaptations amplify his tactical intellect and swordsmanship, mirroring Sapphire’s capabilities. The 1967 anime subtly refines his past to underscore resilience and ethical fortitude, while stage productions preserve iconic moments: a fateful dance with Sapphire’s disguised self and the duel that sparks the kingdom’s unraveling.

Beyond the original manga, anime, and stage iterations, his presence in spin-offs remains unexplored. His arc closes with Silverland’s liberation and union with Sapphire, resolving both personal struggles and the external forces that sought to divide them.