G5 is a large cybernetic robot that has the appearance to a samurai. He wears a shiny metallic armor with long shoulder-pads and spiked claws on his forearms. His face is covered in a mask with a slit that reveals a single eye in the center.
G5 has a straightforward, yet secretive personality. He only speaks when he has a question or when the situation is appropriate, otherwise he remains quiet. He appears to mind his own business unless he wants to add his thoughts that would be beneficial to the situation.
As a robot, he thinks rationally and not impusively. He offers his idea of using Narinki's mercenary group as an advantage for the Monster Association instead of killing them.
He also seems to have some intolerance towards some of the monsters. He questioned Gyoro Gyoro if monsters could kill one another, focusing on Royal Ripper's murderous attitude towards his supposed allies.
Human Monster SagaEdit
Monster Association ArcEdit
On his way to join the Monster Association on behalf of the Organization, he coincidentally ran into Narinki's mercenaries group and captured them, bringing them to the Monster Association. When questioned about who he was by Gyoro Gyoro, he told him that The Organization had sent him to join the Monster Association, probably to help them bring the Hero Association down; when Gyoro Gyoro asked him what The Organization exactly was, G5 kept quiet.
As the Monster Association were deciding what to do with the mercenaries, G5 stepped in and convinced Gyoro Gyoro to use them as their fodder, because of their special battle suits. Gyoro Gyoro agrees and Do-S makes them her love slaves. 
He encounters Royal Ripper and The Great Food Tub as they are arguing over Tareo, promptly grabbing a nearby monster to throw at Great Food Tub's mouth in order to quench his hunger; Royal Ripper notices he is carrying something, which G5 explains is a "hobby of his". The object in question turns out to be the head of the Metal Knight combat unit that followed Elder Centipede on his way back to the monster's hideout; G5 says he kept it because it is "a precious sample" he wants to examine in detail.
After the S-Class heroes invade the Monster Association Headquarters, G5 encounters Child Emperor and Waganma after destroying the former's Radio-Controlled Sentry. He is able to resist the attacks of Child Emperor's Enemy Machine Disabling Device: Bug Kun and swiftly destroy it. G5 battles the newly combined Underdog Man, Mad Dog Underdog Cerberus, while hampered by Child Emperor's bird lime missiles. As G5 battles Mad Dog Underdog Cerberus, Child Emperor and Waganma escape.
Abilities and PowersEdit
As a Demon-level threat and a "machine god", much like G4, it can be assumed that G5 is a powerful Mysterious Being. It is assumed that he is an upgraded version of his predecessor and thus significantly stronger than it. Additionally, despite only being a Demon-level monster, his design was advanced enough to remain unaffected by Child Emperor's technology, and the hero went so far as to say that it would be a time-consuming effort to defeat him.
Immense Durability: G5 was able to completely negate the effects of a trap device specifically made by Child Emperor to shutdown machines.
Extendable Arms: G5 can extend his arms.
Enhanced Speed: G5 has quick reactions as he was able to rapidly extend his arm to grab a nearby monster and throw it at the Great Food Tub's mouth as a substitute meal.
Expert Swordsman: While his actual combat prowess is currently unknown, it is likely that G5 is skilled at sword fighting based on it possessing a pair of katanas.
Katanas: G5 is equipped with two katanas.
Claws: G5 is also equipped with two claws in his hands.
- ↑ One-Punch Man Manga; Chapter 86, page 9
- ↑ One-Punch Man Manga; Chapter 86, page 8-10
- ↑ One-Punch Man Manga; Chapter 86, page 16-20
- ↑ One-Punch Man Manga; Chapter 89, page 53-56
- ↑ One-Punch Man Manga; Chapter 97, page 32
- ↑ One-Punch Man Manga; Chapter 98, page 9
- ↑ One-Punch Man Manga; Chapter 98, page 8
|Executives||Orochi • Psykos • Gyoro Gyoro • Black Sperm • Evil Natural Water • Homeless Emperor • Fuhrer Ugly • Gums • Overgrown Rover • Nyan • Elder Centipede • Gouketsu|
|Dragon||Gale Wind • Hellfire Flame • Phoenix Man|
|Demon||Awakened Cockroach• Bug God • Devil Long Hair • Do-S • G5 • Hundred-Eyes Octopus • Pureblood • Rafflesidon • Royal Ripper • Senior Centipede • Face Ripper • Fist Fight Djinn • Free Hugger • Rhino Wrestler • The Three Crows • Showerhead • Super Mouse • Unihorn • The Great Food Tub • Vacuuma|
|Tiger||Destrochloridium • Electric Catfish Man • Maiko Plasma • Marshall Gorilla • Sludge Jellyfish|
|Unknown||Eyesight • Gyoffrey • Goddess Glasses • Venus Mantrap • Junior Centipede • Haragiri • Rosie • Choze • Benpatsu • Hamukichi • Volten • Evil Eye • Gale • Hellfire|