Juan Diaz serves as captain and star midfielder for the Argentina national youth team, hailed as a prodigy succeeding Diego Maradona and bearing the weight of expectation as Argentina's next-generation football superstar. His playing style is defined by exceptional speed and dribbling skills, most famously demonstrated by the "8-men-in-succession dribble" where he maneuvers past multiple opponents, including the goalkeeper. Initially characterized by arrogance and conceit, Diaz exhibits supreme confidence in his superior abilities. This attitude evolves following intense matches against Japan and direct clashes with rival Tsubasa Ozora, resulting in a more tempered demeanor while preserving his fierce competitive drive. A significant rivalry blossoms with Tsubasa, fueled by their comparable talents and mutual influence on each other's technical development. His technical arsenal includes the Drive Shot, Banana Shot, Diving Header, Forward Somersault Shot, and Overhead Kick. After observing Tsubasa's Cyclone technique, Diaz develops his own variations. Depending on match circumstances, he masters techniques such as the standard Cyclone, Neo Cyclone, Backward Somersault Cyclone, and Heel Lift Cyclone. He also executes combination plays with teammate Pascal, notably the "Golden Combi" and "Argentina Combi." A hidden passive ability, "Proof of Genius," occasionally enhances his stats and dribbling speed during matches. Within the narrative, Diaz captains Argentina to qualify for the International Junior Youth Tournament, scoring the decisive goal against Uruguay in the South American World Youth preliminaries. Argentina meets Japan in the tournament's knockout stage, where Diaz witnesses Tsubasa unveil the Cyclone technique; Japan wins the encounter. Later, during the Universal Youth tournament, Argentina faces Japan again. Diaz initially dismisses the match due to Tsubasa's injury absence, but Japan prevails under Jun Misugi's leadership. Transitioning to a professional career with Argentinos, Diaz's development of the Cyclone technique diverges based on match outcomes: he may learn the Neo Cyclone or create the Backward Somersault Cyclone variant. As captain, he leads Argentina to Copa America victory over Brazil, though Brazil regains the title in the subsequent tournament. Diaz later confronts Japan again in a World Tournament semifinal, deploying his mastered Heel Lift Cyclone technique during the match. His character arc demonstrates adaptation and growth. He studies and incorporates techniques observed from rivals like Tsubasa, while simultaneously inspiring others; Tsubasa's development of the Neo Cyclone draws inspiration from Diaz's Forward Somersault Shot. Conversations in game data indicate narrative intentions, though not always fully realized across all story routes, for Diaz to consistently learn the Cyclone technique.