Leon is a lion and the captain of the Winners team, Elevenia's reigning national soccer champions renowned as the league's "winning eleven." He stands as one of the most formidable athletes in a fantasy world where humans and anthropomorphic dinosaurs coexist. His narrative significance begins when he challenges Amon, Tokio's father, to a high-stakes one-on-one soccer match. After defeating Amon in a close contest, Leon enforces their pre-match agreement, transforming the loser into a miniature dragon. This act sparks Tokio's quest to restore his father's human form by competing in the Dragon League tournaments.

As a primary antagonist, Leon represents the pinnacle of soccer prowess that Tokio and his Junior Winners team must overcome. Their teams clash in the Dragon League professional tournament finals during the series' second arc. Despite his team's reputation and skill advantage, Leon suffers defeat against Tokio's squad. This loss marks a significant turning point, after which his prominence in the narrative diminishes. As the story shifts focus into a fantasy-driven third arc involving a world-threatening conflict with the Golden Dragon, Leon's role becomes minimal. The hinted rivalry between Leon and Amon goes unexplored. Following his defeat, Leon also fades from the soccer scene.