Kazuto Hijiri emerges as the protagonist's primary rival within the racing narrative. Possessing significant wealth and exceptional driving talent, he is romantically involved with Junko Komori. Their rivalry ignites during an initial encounter on public roads, where Hijiri witnesses the protagonist driving a modified tractor from behind the wheel of his BMW. This moment establishes Hijiri as the benchmark for the protagonist's motorsport aspirations.

Hijiri harbors the ambition of reaching Formula 1, representing a contrasting background and approach to racing compared to the protagonist. His career path progresses through junior categories, notably Formula 3. During this ascent, Hijiri strategically recruits Tamotsu Oishi, the protagonist's mechanically gifted friend. This move creates professional tension, intensifies the rivalry, and occurs amidst familial conflict involving the protagonist, further complicating relationships.

A concealed brain tumor forms a significant aspect of Hijiri's character. This condition poses a constant threat to his racing career and personal safety, yet he persists in competition. The tumor influences his decisions and heightens the dramatic stakes, particularly during high-level races. His participation in Formula 3 serves as the narrative's competitive focal point, culminating in a major confrontation with the protagonist that tests both drivers' capabilities and resolve, with the medical condition remaining an underlying factor throughout.