Genos is Saitama's disciple, he wishes to become strong
Up until the age of Fifteen, Genos was a normal young man who lived with his family. This ended when a deranged cyborg attacked his town, killing most of its inhabitants, including Genos' parents. He was subsequently found and saved by a virtuous scientist named Dr. Stench who had been pursuing the renegade scientist. Wishing to put an end to the creature that cost him so much, Genos begged the scientist to turn him into a cyborg. Stench complied, and Genos has spent the succeeding four years seeking the cyborg. Having witnessed Saitama's awesome physical prowess, Genos asked to become his disciple, hoping that by learning the secret of the bald hero's strength he might acquire the might to avenge his family.
The mangaka "ONE" created Genos for his webcomic One-Punch Man in 2009. In 2012, ONE was approached by Yusuke Murata to consider a collaboration between the two, and the One-Punch Man remake, which also features Genos, was the result.
Genos is a fair-haired and good-looking young man with yellow irises and black sclera.Most of his body appears to be robotic, and while he usually wears common casual clothes like hoodies and jeans, he often leave his metal arms bare.
Genos is a very serious-minded person, very driven, and focused on avenging his family and fighting evil. In many ways he could be seen as an idea hero - selfless, brave, modest and with a strong sense of justice.
Since moving in with Saitama, he has grown quite devoted to him, and has a tendency to hero-worship him, and can become quite angry when he feels that his reluctant teacher isn't shown the respect he deserves.
Genos has a powerful cyborg body with many devices built into it. This grants him considerable physical strength, speed and especially endurance, as well as an impressive array of weaponry including lasers and flamethrowers. He is also an intelligent, clear-thinking individual with excellent fighting skills. All of this would seem to make Genos an incredibly formidable and successful hero, however, he is very often defeated, very badly injured into the bargain, and needs his mentor Saitama to bail him out.
Fortunately for Genos, he finds his cyborg body easy to maintain and repair.