- Gender: Male
- Age: Unknown
- Hair: Black/Variable
- Eyes: Red
- Nationality: Probably Japanese
- From the manga Biobooster Armor Guyver, by Yoshiki Takaya
- First Appearance: Chapter 12
Extremely little is known about the Lost Unit Aptom. Designed as a zoanoid able to perfectly mimic the appearence and abilities of any opponent, Aptom never quite lived up to expectations. His imitations, while similar, were never quite perfect replicas of his chosen targets. More problematically still, he mutated unpredictably during the zoanoid processing, and thus his type could never be reproduced, making him a despised failure to most of Chronos. The mutation is most likely the cause of the distinctive scar which runs down the side of his face, as well.
His only friends are the other Lost Units, particularly Somlum and Dyme. Their close bond is what allowed them to live through the inhuman experimentation and cruelty of Chronos, but unfortunately, Somlum was recently killed during an attempt to kidnap an enemy of the organisation.