Antoine, the French localization of Jun Randou, is the youngest son in a treasure-hunting family. Approximately fifteen years old, he acts as an audience surrogate for younger viewers. As a deuteragonist, Antoine frequently drives central plot developments in individual episodes, though his older brother Hiro occasionally overshadows him in narrative focus and heroic moments.

He dons a distinctive fedora—visibly contrasting with his father’s trilby—aligning him with classic adventure archetypes. Antoine pilots the Buncher Arrow motorcycles, component vehicles that combine into the super robot Acrobunch. He is additionally trained to operate the Falcon Buncher jet during combat when his father is unavailable.

His characterization balances youthful impetuousness with flashes of responsibility for relatability. While his brothers Hiro and Ryo display clearer bravery and comic relief traits respectively, Antoine often engages directly with mythological or historical mysteries during the global quest, positioning him as the adventure’s "Young Indiana Jones" analogue.

The French adaptation relocates the family’s base from the Japanese Alps to the Canadian Rockies and changes their surname from Randou to Cossyg. Antoine’s experiences, background, and relationships remain contextually identical to Jun’s, reinterpreted solely within a Francophone setting without storyline divergence.

His consistent narrative arc involves hunting the legendary Quetzalcoatl treasure while battling the subterranean Goblin Society. Antoine undergoes no major personal transformations exclusive to the French version, and his entire journey—including climactic events—mirrors Jun’s original Japanese portrayal. His appearances are confined to the core 24-episode series.