Retsu Seiba, an 11-year-old fifth-grade student and older brother of Go Seiba, balances patience and strategic thinking against his sibling’s impulsiveness, though he occasionally reveals flashes of frustration when challenged. His visual identity centers on red—expressed through his hair, eyes, gloves, and shirt—while his iconic green hat adds a contrasting hallmark.

A specialist in Mini 4WD cars from the Sonic series, Retsu employs vehicles optimized for off-road adaptability and balanced performance, mirroring his meticulous racing philosophy. As captain of the TRF Victorys during the World Grand Prix, he steers the team through global challenges against rivals such as Italy’s Rosso Strada and Germany’s Eisen Wolf. His growth lies in harmonizing team dynamics with personal accountability, evolving from a competitive brother to a steadfast leader.

The sequel *Return Racers* depicts his shift from racing when mentor Dr. Tsuchiya facilitates his entry into a space development initiative, highlighting his technical ingenuity and adaptability. While his bond with Go matures into mutual encouragement, their adult trajectories gradually separate.

Interactions with allies like Ryo Takaba and Tokichi Mikuni refine his collaborative instincts, and his technical skill paired with unflappable poise establishes him as the TRF Victorys’ anchor. Retsu’s narrative weaves competitive racing, self-discovery, and post-racing scientific endeavors, intertwining youthful passion with mature ambition.