Biitoma hails from Pluster World's Kabuto Tribe, a realm inhabited by mechanical Plusters. His driving ambition to become the most powerful Pluster compels him on a significant journey. During this quest, he encounters Wyburst of the Grip Tribe and clashes with a Minus-Beast. Defeated in battle, Biitoma is accidentally hurled into the human world.

There, he forges a vital partnership with Tohma Kaname, an 11-year-old human seeking vengeance against the same Minus-Beast that overwhelmed Biitoma. This alliance enables Biitoma to merge with Tohma through "plusting," dramatically amplifying his combat strength. This fusion unlocks advanced forms like Beetma EX for critical battles.

Initially fueled by personal revenge, Biitoma's focus broadens. He allies with Wyburst, who searches for the legendary Gonggorahgong artifact, believed capable of restoring Pluster World's peace. Together, they lead a diverse group of allies, including Plusters like Harnia and Moley, to confront the resurgent Minusters threatening their world.

Biitoma evolves from a solitary fighter into a cooperative leader. His bond with Tohma deepens beyond combat utility, fostering mutual reliance and trust. This relationship becomes central to his growth as they face escalating threats, including the pursuit of the destructive Gigajoules entity and battles within Gorago's Castle.

Throughout their journey, Biitoma contends with internal and external challenges, such as temporary separations from Tohma and conflicts testing their unity. These experiences cement his commitment to protecting Pluster World and solidify his role within the team. By the quest's culmination, Biitoma's pursuit of individual strength transforms into a dedication to collective peace and the well-being of his allies.