After the suicide of his abusive father, young Riku Azami is taken in by his mother, who lives with a violent yakuza member. When Riku angers his mother's intoxicated boyfriend, a life or death struggle ensues and Riku kills the man in self-defense.

After this incident, Kyousuke Tokorozawa, a former boxer and yakuza member, notices Riku's fighting potential and introduces him to the world of boxing. Etched with trauma from being beaten and nearly murdered, Riku hardens his resolve to fight. Despite his aloof demeanor, Riku discovers many things to fight for—including his caring childhood friend, Yuki Naeshiro.

Years later, after training at the famous Baba Boxing Gym, Riku discovers an innate desire to rise to the top. Now, as a professional boxer, 18-year-old Riku is determined to earn the prestigious Oriental and Pacific Boxing Federation belt and become a boxing champion.