Genos

Genos's serious demeanor. Genos is an extremely serious character, rarely if ever making jokes. He constantly strives to become stronger and often seeks Saitama's guidance to achieve his ambitions. Since becoming Saitama's disciple, Genos shows deep reverence and protectiveness towards him, referring to Saitama as "master." While he both admires and envies Saitama, he still feels frustration and disbelief at Saitama's seemingly simple training regimen, which somehow resulted in extraordinary strength. Occasionally, Genos acts as a comic foil to Saitama's oblivious nature. He frequently employs advanced techniques, battle strategies, and robotic upgrades to fight villains, often sustaining severe damage, only for Saitama to defeat the same enemies with a single effortless punch. Convinced that there is a secret behind Saitama's immense strength, Genos is motivated to observe him closely to uncover this mystery. Initially more intense in his pursuits before meeting Saitama, Genos has become slightly calmer due to Saitama's influence, adopting a more measured approach to justice and power. He recognizes his growth when he witnesses Sweet Mask ruthlessly dispatch a group of alien prisoners, reflecting on how similarly unyielding he once was. Gradually, Genos has become less serious and even curious about minor aspects of life, such as the meaning of fun. Genos holds deep respect for two individuals: Saitama and Dr. Kuseno, the man who saved him. He extends professional respect to those who display genuine expertise, such as Bang and Bomb, and tolerates individuals like King, whom Saitama willingly spends time with. However, he exhibits jealousy towards Overgrown Rover when Saitama pets the dog or calls it by name. He shows little to no hesitation in eliminating individuals he deems dangerous threats, even if they are still humans or criminals. One particular example is Garou; during their battle, he didn't seem to try capturing Garou alive but instead appeared more intent on eliminating him as he would a monster. Genos tends to be disrespectful towards most others, particularly those who interrupt or annoy Saitama. Whenever Bang or Fubuki command him or attempt to recruit Saitama, Genos interrupts and demands they get to the point. He staunchly defends his role as Saitama's disciple, actively discouraging Saitama from forming close relationships with others. This hostility extends beyond those who offend Saitama; it also includes Dr. Kuseno. Genos has even called out Saitama for calling Dr. Kuseno an old man, though he quickly apologized. Genos shows little respect for the Hero Association's authority, informing Sitch that he would have joined the Monster Association raid regardless of whether he was part of the main task force, stating that his actions are independent of the Hero Association's decisions. Genos takes pride in his abilities and himself. During his battle with Awakened Cockroach, he feels frustrated for having to use instant adhesive gel, which forces him to acknowledge that there are monsters faster than he is. However, his fights against G4, Face Ripper, Awakened Cockroach, and Garou demonstrate that he values strategy alongside raw power. Before becoming a cyborg, Genos was also serious, described by ONE as a diligent and responsible boy from a young age. While pursuing Bofoi, Genos reflects on the fact that he has always known Bofoi is dangerous, yet questions why he allowed him to go unchecked for so long. As he considers what clouded his judgment, memories of Saitama's casual moments flash in his mind, suggesting Saitama's influence may have played a part. However, Genos resolves not to blame Saitama or anyone else for this oversight.

Genos is a mechanical cyborg of average human height. His face and ears look like that of a normal human, made of artificial skin material, and his eyes have black sclera with yellow irises. He has spiky blond hair and his eyebrows are blond (brown in the anime). He also has pierced ears. Genos's wardrobe consists of street clothes with all of his upper-body attire being sleeveless as to allow his arms to transform without hassle. He has many different sets of arms, with varying abilities and strengths. Notable examples of his various "arms" are those he used in his sparring match against Saitama and the arms he equipped to combat the meteor. Sometimes the arm sets he uses create a metal framing around his face, like when utilizing Arms Mode and in his Monster Association Arc Upgrade. During his fight against the Forest King, he has an upgraded body, which exposes the energy core in his chest.