Genos' Core

Genos runs on a single orb of energy simply labeled Core, mounted in his chest and tied to his body through one cable. It supplies all of his power and effectively serves as his heart, which makes it a fatal weak point. Strip it out or break it, and the cyborg dies. Later events reveal that the sphere is in fact a compact nuclear reactor.

Beyond keeping Genos alive, the core can be pushed to extremes. Cornered by Mosquito Girl, he charged it to detonate and take her down with him, and against an incoming meteor he pulled it from his chest, slotted it into his arm, and funneled every bit of its output into his Incineration Cannon for a decisive shot.

The core also acts as a recorder, logging its surroundings even after Genos has died. That property let it carry the memory of the Ominous Future back through time alongside Saitama and pass those events on to a living Genos. A newer upgrade lets him vent the core's energy as a blinding flash of light, which he tries out on Saitama during a sparring rematch.

Dr. Kuseno engineered the core, and it powers Genos alone. It has changed hands only under unusual circumstances, such as when a version of it recovered from a doomed timeline was carried back into the present.