Kyoma Gun is a 17-year-old motorcycle racer distinguished by his exceptional speed and fierce competitive spirit. He first gains recognition within Japan's underground racing scene through illegal street racing on mountain passes, known as tōge. As part of the "rolling-zoku" subculture, he rides a customized Honda CB750F cafe racer, establishing his reputation among peers and rivals.

Gun attends high school alongside key individuals shaping his trajectory. Classmate Hideyoshi Hijiri evolves from his primary rival to a collaborative partner, culminating in their joint participation in the Suzuka International Racing Course endurance race—marking Gun's shift toward professional competition. Hiro Okita serves as Gun's closest friend and racing companion, providing consistent support during events. Ai Itou is documented as Gun's romantic partner.

Gun transitions from illicit racing to formal circuit competition, progressing to advanced machines like the Suzuki GSX-R. He competes in professional events including the All Japan Road Race Championship, demonstrating technical growth in refined riding postures, precise steering, and adaptive race strategies. He adopts the racing number 56 during this phase, a detail later mirrored by real-world professional racer Shinya Nakano as homage.

Gun's personality blends intense competitiveness with deep loyalty, particularly evident in pivotal collaborations like the Suzuka race with Hideyoshi. His story incorporates dramatic racing incidents, including high-impact crashes that underscore the sport's physical risks.