Kappei Jin is the main character of Zambot 3 and pilot of the Zambird/Zambo Ace as well as controlling the primary functions of the titular robot. At 12 years old, Kappei is always eager to get into dangerous, high-risk situations, be it in battle against one of Gaizok's Mecha Boosts or against his rival Kōzuki.

While Kappei is generally willing to go into battle, he will at times run into an emotional dilemma, generally stemming from civilian backlash against him and the other survivors from Planet Beal. Kappei is also very athletic and a skilled martial artist.

His best friends are his pet robot dog, Chūnishiki and the girls Aki and Michi.