Tokichi Mikuni, heir to the prominent Mikuni Corporation, initially embodies a spoiled and manipulative personality. He exploits his family's vast wealth and others' vulnerabilities during races, employing cheating tactics and financial advantages that lead to confrontations with figures like the Seiba brothers, his butler, and his father. A pivotal defeat by Retsu Seiba sparks self-reflection, prompting a gradual shift from his entitled behavior. While evolving into more of a comic relief role, he retains a playful and occasionally tricky demeanor, sometimes compared to a monkey in both actions and appearance. His distinct speech includes pronouncing "desu" as "degesu".

As a racer, Mikuni specializes in cornering machines engineered for technical precision. His signature techniques, Thunder Dribble and Lightning Dribble, grant his cars exceptional handling through complex sections like zig-zags, chicanes, and hairpins. His primary machines include the Spin Axe (developed by Professor Tsuchiya), the Spin Cobra (his main WGP season car featuring both Dribble techniques), and the Spin Viper (debuting successfully against the Australian Boomerangs). In *Return Racers!*, he pilots the Spin Axe Zero.

Mikuni's character develops significantly throughout the series. Joining the TRF Victorys team in the WGP arc marks his transition toward cooperation and sportsmanship. By *Return Racers!*, he assumes the presidency of the Mikuni Corporation, balancing corporate leadership with continued Mini 4WD racing. Relationships evolve alongside this growth; once a rival to the Seiba brothers, he becomes their ally and friend. His younger sister, Chiiko Mikuni, occasionally disrupts his plans, including during an incident involving Kai Okita's attempt to take over a Mikuni game center.