Kojiro Hyuga's childhood was defined by financial hardship and his father's absence, driving him to support his family through strenuous part-time jobs at fruit and seafood markets, which built his exceptional physical strength. These early struggles forged an initially cold-hearted, reckless, and intimidating persona on the football field, earning him the "Fierce Tiger" (Moko) nickname for his untamed aggression. Yet beneath this roughness, he consistently showed deep care and loyalty toward his family, close friend Takeshi Sawada, and later his girlfriend Maki Akamine. His football journey began at Meiwa Elementary School, where he wore jersey #10, and flourished at Toho Academy with a V-4 high school championship. As a forward and ace striker, he became known for his powerful, physical style and signature Tiger Shot—a strike mimicking a charging tiger. This technique evolved into the Neo Tiger Shot and combo moves like the Toho Twin Shot with Sawada and the Neo Drive Tiger Twin Shot with Tsubasa Ozora. His skills expanded to include the Straight Line Dribble and Raging Wave Tackle, reflecting his growth beyond a pure finisher. Initially positioned as Tsubasa Ozora's primary rival—symbolized by their black-versus-white attire and raw power versus technical finesse—Hyuga's relationship shifted from antagonism to mutual respect and collaboration. This culminated in their partnership on Japan's national team, where he wore jersey #9. Key developments included his leadership in motivating the team during Tsubasa's injury and coordinated international plays, such as forming the Meiwa Combi two-top forward combination with Genzo Wakashimazu during the Rising Sun arc. Pursuing his dream to become the world's best striker, Hyuga moved to Italy, signing with Juventus (later represented as Piemonte). Facing intense competition, he was loaned to Serie C's AC Reggiana. In a critical promotion battle against Shingo Aoi's FC Albese, he scored a decisive hat-trick using his Raiju Shot, securing Reggiana's promotion to Serie B and showcasing his resilience overseas. In later developments, Hyuga returned to Juventus/Piemonte in the NEXT DREAM storyline to reclaim his elite status. He balanced on-field ferocity with off-field responsibility, exemplified by his leadership in Japan U-23 campaigns during the Rising Sun arc, where he vowed early goals to prove the team's capability. Throughout his career, Hyuga's defining traits included unwavering ambition, self-confidence, and a relentless drive to overcome obstacles. His journey reflected a progression from solitary toughness to team-oriented play, underpinned by enduring loyalty to those closest to him.