Genos, a 19-year-old cyborg, serves as the deuteragonist across all official media. His human life ceased when a rogue cyborg annihilated his hometown and family, leaving him critically injured. Rescued by scientist Dr. Kuseno, who pursued the same assailant, Genos underwent full-body cyberization in exchange for aiding Kuseno's hunt. This tragedy forged his dual drive: vengeance against the killer and a commitment to justice. Intensely serious and rarely humorous, Genos relentlessly pursues power through grueling training and technological enhancements. After witnessing Saitama effortlessly defeat Mosquito Girl, he becomes the hero’s self-declared disciple, convinced Saitama possesses unparalleled strength. Genos refers to Saitama as "master" with near-devotional reverence, displaying protectiveness or jealousy toward others interacting with him, like Overgrown Rover or Fubuki. Though typically stoic, Saitama’s influence gradually softens his rigidity, sparking curiosity about concepts like "fun" and prompting self-reflection when observing others’ ruthlessness. He reserves respect solely for Saitama and Dr. Kuseno, reacting with indifference or hostility toward most, especially those interrupting Saitama or challenging his disciple role. As the S-Class Rank 11 hero "Demon Cyborg," Genos wields formidable combat capabilities via his cybernetic body. His chest houses a nuclear core reactor powering all systems and recording environmental data post-mortem. Cybernetic augmentations grant immense strength—shattering terrain and rivaling top heroes—and supersonic speed, demonstrated against foes like Speed-o'-Sound Sonic. His endurance bypasses organic vulnerabilities, fighting through dismemberment, radiation, or catastrophic damage, though acidic corrosion induces pain. Primary armaments include palm-mounted Incineration Cannons firing mountain-vaporizing plasma, plus modular units like "Arms Mode" for amplified strikes. Tactical adaptations feature adhesive gel for immobilizing swift enemies and rocket boosters for aerial combat. Kuseno’s continuous upgrades culminate in post-Elder Centipede enhancements enabling solo victories against Dragon-level threats. Genos evolves strategically: initially reliant on brute force, defeats against adversaries like Awakened Cockroach or Garou push him toward analytical tactics, gadget integration, and environmental exploitation. Combat logs show a 70% success rate against Demon-level threats early on, later rising to consistent Dragon-level engagements. He functions as Saitama’s tactical foil, meticulously documenting battles only for Saitama to resolve them instantly. Genos anchors the "Saitama Group," an informal alliance with King, Bang, and Bomb. Key arcs involve collaborative Monster Association battles, where he confronts Garou and Elder Centipede alongside martial arts masters. Cosmic Garou kills him to provoke Saitama, but Genos retains memories after Saitama resets the timeline. Post-arc, he relocates to the Hero Association headquarters following City Z’s destruction, investigates the Neo Heroes, and receives a final upgrade from Kuseno before the scientist’s assassination. His core data proves pivotal against existential threats like "God." Genos’s physiology allows food consumption for biofuel conversion, though his weight prevents swimming without specialized parts. Despite mechanical components, he retains human traits like taste perception and participates in social activities, such as hotpot meals with Saitama’s group.