Rupert von Trapp, the 14-year-old protective eldest son of Baron Georg von Trapp, shoulders responsibility for his six younger siblings. Skilled in fencing, he hones his disciplined nature through rigorous practice while balancing his role as a peacemaker and problem-solver. He takes charge of resolving sibling disputes and household tasks, such as repairing a damaged skiboard during a critical moment.

His combative dynamic with Anton, a rival-turned-respected peer, climaxes in a rain-drenched fencing duel outside the family estate. Though initially adversarial, their relationship shifts when Anton relocates to Russia, fostering grudging admiration. Concurrently, Rupert navigates a complex friendship with Nastassja Ivanovna, a figure unique to the anime who becomes a point of mutual interest between him and Anton.

As political tensions escalate during Austria’s annexation, Rupert’s defiance against fascism crystallizes—he shreds a swastika flag with his father’s naval dagger in a bold act of rebellion. When the family flees, his ingenuity surfaces as he devises a plan to conceal younger siblings in a coffin to bypass Nazi patrols.

Rupert evolves from a competitive teenager into a morally steadfast figure, confronting covert threats like Hans, the family butler and Nazi informant. These clashes sharpen his political awareness and reinforce his loyalty to his father’s anti-fascist principles, solidifying his role as both guardian and symbol of resistance.