G5

In its outer shell G5 takes the shape of a towering samurai-like automaton sheathed in gleaming metal, with wide shoulder guards, spiked claws along its forearms, and a single glowing eye peering through the slit of its mask. A crescent-moon helmet bristling with spikes crowns its head, and marks resembling an X trail down its armor. Strip that away and the real G5 is a compact, rounded robot in black plating, its dome-like head fused into its chest, mechanical joints left exposed, and four-fingered hands.

G5 is terse and guarded, speaking only when it must and otherwise keeping to itself, though it will offer input when doing so serves the moment. Its true loyalty lies with The Organization, and it faithfully cooperates with the Monster Association while never once betraying its real allegiance. It reasons coldly rather than acting on impulse, proposing that Narinki's captured squad be exploited as an asset instead of killed. It shows little patience for certain monsters, pressing Gyoro Gyoro on whether members may kill one another and singling out Royal Ripper's aggression toward allies, and a streak of pride leads it to believe that mimicking Atomic Samurai's swordsmanship would be enough to beat him.

Sent to reinforce the Monster Association on The Organization's behalf, G5 runs into Narinki's Private Squad along the way, seizes them, and hands them over. It stays silent about its true masters when Gyoro Gyoro interrogates it, then talks the leader into deploying the captured mercenaries as disposable troops for their special battle suits, whom Do-S promptly enslaves. It later keeps a severed Metal Knight unit head as a study sample and casually feeds a stray monster to The Great Food Tub to settle a dispute.

When the S-Class heroes storm the headquarters, G5 confronts Child Emperor and Waganma, shrugging off the boy's machine-disabling trap and smashing it apart before tangling with the fused Mad Dog Underdog Cerberus while birdlime missiles rain down, letting the pair slip away. Having beaten Cerberus, it faces Atomic Samurai, boasting that it has learned to mirror his Atomic Slash, but even wielding twin blades and his own signature move it is hopelessly outclassed, its armor and swords carved to pieces, though its core escapes. It resurfaces to blast Sekingar's hand off and stop him radioing the Hero Association, only for Genos to appear and crush the little core underfoot. Its edge in battle came from analyzing and replicating enemy techniques, aided by double-jointed limbs that let it strike from impossible angles, though its predictions faltered against anyone concealing their real strength.