Jiromaru Takaba is the younger brother of Ryo Takaba. The brothers live a nomadic lifestyle, frequently camping in wilderness areas and fending for themselves without adult supervision. Jiromaru has long brown hair reaching his shoulders and brown eyes. He typically wears a pink shirt, brown gloves, long brown pants, white-pink shoes, and an orange headband like his brother. His height is 115 cm (approximately 3'9") and weight is 23 kg (approximately 51 pounds). His birthday is March 25, making him an Aries, with blood type B.

Jiromaru exhibits strong admiration and protectiveness toward Ryo, following him constantly and defending him against perceived insults. Their dynamic highlights mutual reliance. His speech includes frequently mispronouncing the Japanese copula "desu" as "dasu". He addresses Ryo using the affectionate term "anchan", a blend of "oniichan" and "aniki".

His primary hobby is cooking. Jiromaru often clashes with Go Seiba, engaging in mutual mockery typically stemming from competitive dynamics or disagreements involving Ryo. As a Mini 4WD racer, he pilots a car named "Jiromaru Special", sharing design similarities with Ryo's Tridagger X. His racing career involves frequent damage to his vehicles. During the WGP season, he substituted for an injured Ryo but experienced stage fright before the race due to the event's scale.

An early story arc revealed a tendency toward underhanded tactics; he once rigged a race track to make his lane easier than those of Retsu and Go Seiba. This strategy backfired when the brothers won regardless. Despite his initial introduction, Jiromaru's role diminishes over time as narrative focus shifts toward Ryo and other racers.

Later media such as the MAX season, movies, OVAs, or the Return Racers spin-off manga do not feature him. Similarly, no details exist about his activities or whereabouts in later timelines like the Return Racers era where Ryo pilots the Tridagger WX.