Genos

Genos is a mechanical cyborg of average human height. His face and ears resemble those of a normal human, made of artificial skin material, and his eyes have black sclera with yellow irises. He has spiky blond hair and blond eyebrows. He also has pierced ears. Genos's wardrobe consists of street clothes, and all upper body clothing is sleeveless to allow his arms to transform seamlessly. He is 178 cm (5'11") tall.

Clean and tidy the apartment + follow Saitama + do justice + help the citizens of Z City + defeat monsters + train + upgrades + cook

Full Cyborg Armament + Flight + Fire Manipulation + Electricity Manipulation + Energy Projection + Self-Destruction + Highly Skilled and Strategic Combatant Serious + Able to remain calm in critical moments + Use his own cyborg body as a weapon + Able to shoot fire from his arms and hands

Genos has an extremely strong and serious character. He constantly strives to become more powerful by frequently asking Saitama to train him. Since becoming Saitama's disciple, Genos is very reverent and protective towards his "sensei", greatly admiring and respecting him and can be quite accommodating towards him; although there are times when he expresses disgust and disbelief at the mundane training regimen Saitama used to gain his strength.

For the most part, Genos acts as a comic book foil to Saitama's clueless antics, using a variety of special techniques, battle tactics, and robotic upgrades to battle monsters and villains (taking horrific damage in the process and on one occasion nearly dying), only to be bested by Saitama with a single punch. Due to Saitama's incredible strength, Genos becomes led to believe that there is a secret to Saitama's power.

Despite their disparity in strength, Genos gains greater recognition than his mentor. His superior acumen immediately granted him the status of an S-Class hero within the Hero Association, compared to Saitama's C-Class designation. He also apparently possesses a large sum of money, enough to repair and upgrade his cyborg body whenever it returns destroyed from combat and to cover Saitama's rent on a regular basis.

Over time, he softens, and he acknowledges that this is due to Saitama's influence. Eventually, he comes to respect Saitama not only for his power, but also for his character. This is shown when Genos comments on how similar he was in his past to Amai Mask, before he met Saitama, by having no mercy in his heart and annihilating both monsters and villains in cold blood. Genos slowly becomes less serious and becomes slightly curious about some minor things like the meaning of fun.

Surprisingly, he is quite disrespectful to those who interrupt Saitama or constantly bother him, as whenever Bang or Fubuki order him around or try to recruit Saitama, he will continually tell them to get to the point and defend his position as Saitama's disciple, and nothing more. This hostile behavior not only extends to those who offend Saitama, but also Dr. Stench. This is seen when Fubuki asks Dr. Stench to join the Fubuki Group, going so far as to insult her and threaten to incinerate her. Genos even does the same to Saitama when he called Dr. Stench an "old man", but Genos immediately apologized when Saitama told him to calm down.

Genos seems to have a certain sense of pride in his abilities and himself. This is seen in his battle against Smart Cockroach when he shows slight disappointment at having to use the adhesive material on him, as it would force Genos to accept that there were monsters much faster than him. However, his fight with Face Reaper, Smart Cockroach, and Garou shows that he is no longer thinking about raw power and is considering defensive measures. Genos has begun using tricks to gain the advantage in his fights now, though that is usually seen when he has no other choice.

Initially, Genos was a loner who used to fight and confront the kaijin individually, but as the story progressed he began to collaborate more and work as a team with other heroes. He collaborated with Bang and Bomb to defeat the Elder Centipede, also during the Monster Association arc he is seen working alongside Drive Knight and Tatsumaki to defeat Psykos. Even so, Genos remains distant from his S-Class companions and does not usually fraternize with them, but maintains a cordial relationship with some of them such as Bang, King and Drive Knight.