Aptom emerged from the Lost Numbers, a cadre of experimental Zoanoids engineered by Chronos and deemed failures for lacking standardized Zoanoid capabilities. Branded mutations, he endured relentless experimentation and perilous missions alongside comrades Somlum and Dyme, forging an unbreakable bond through shared trials. This kinship defined him as contempt from standard and Hyper Zoanoids intensified his resentment toward Chronos.

During an ambush on Sho Fukamachi, host of Guyver I, Aptom watched Somlum and Dyme fall to Sho’s attacks, igniting an unrelenting vendetta. Mortally wounded, he was subjected to radical reprocessing by Zoalord scientist Dr. Barcas, which augmented his regeneration—enabling recovery from near-total disintegration—and bestowed DNA absorption to mimic Zoanoid abilities. These upgrades also severed his telepathic link to the Zoalords, freeing him from their influence.

Driven by vengeance, Aptom repeatedly clashed with Sho, once exploiting the youth’s trauma by threatening Mizuki Segawa to provoke Sho’s regained transformation. Surviving a near-fatal Mega-Smasher strike through regeneration, he absorbed Hyper Zoanoid Elegen’s DNA to fully reconstitute himself, openly rebelling against Chronos. Declaring war on higher echelons like Richard Guyot and Archanfel, he further destabilized the organization by generating autonomous clones.

His motives gradually shifted from revenge to questioning Chronos’ exploitation of the Lost Numbers. This existential reckoning led him to covertly shield Sho’s allies, recognizing the organization as the source of his suffering. By absorbing Zoanoids and Hyper Zoanoids, he inadvertently bolstered resistance efforts, even as upgraded foes like ZX-Tole targeted him.

In human guise, Aptom sports a muscular frame, a jagged scar tracing from left hairline to jaw, leather jackets, and sunglasses. His protean true form, reshaping through assimilated Zoanoid DNA, wields chimeric transformations, bio-lasers, and rapid evolution. Tactical ingenuity and adaptive prowess render him a persistent menace to both Chronos and Guyvers, though alliances remain transient and self-serving.

After Relic’s Point’s destruction, Aptom carved a solitary path across Tokyo, monitoring Sho’s circle while evading Chronos. Confrontations with enhanced adversaries like ZX-Tole strained his limits, yet his regenerative and adaptive traits ensured survival. While occasionally aiding Sho against existential threats, he maintained calculated neutrality, balancing personal grudges with opposition to Chronos’ tyranny—his arc culminating in reluctant opposition to their global dominion.