After being called over to Bang's dojo, Saitama learns that Bang got a whole bunch of lobsters from his brother and needs someone to help him eat them. Genos complains about them being called out for something insignificant, and tells Bang to call someone else if he needs help eating leftovers, at which point Saitama tells him to stop, saying that they're helping a lonely old man with his food problem. After Charanko arrives with the vegetables, they start preparing the hotpot while talking about a recent dojo hunter that has been attacking other dojos. Saitama notices that there isn't any cabbage, interrupting the conversation about the dojo hunter, which annoys Charanko. After seeing Saitama look bummed about the fact that there isn't any cabbage, Genos angrily asks Charanko why he planned to make hotpot without cabbage. Saitama tries to say that it's fine, but Genos keeps arguing with Charanko because he does not feel like he even feels sorry for not having bought cabbage. After Charanko challenges Genos to a match, Bang tries to calm down the situation by saying that he will go buy the cabbage, and asks Charanko to get along with the other two.
Genos arrives at Saitama's Apartment to return Saitama's hero suit from the cleaners. Genos accompanies Saitama to the Hero Costume Contest and hands Saitama his registration ticket. Genos witnesses Saitama hand over his hero costume to a boy who had his clothes stolen and Saitama tells the boy to go home. Genos questions how Saitama will partake in the event without a hero costume. Saitama assures Genos as he will wear the T-shirt he won from Mouse Sushi. Genos remains silent about Saitama's clothes. Genos watches Saitama's debut on the stage and is shocked when Saitama declares he will show his special power. A monster alert rings and the monster Game-Berus appears. Saitama destroys the monster. After the contest, Genos discusses with Saitama how even though he lost the contest, the audience was on his side. Genos believes that the whole event was a lesson to teach Genos to focus on skill not appearance. He notes down this lesson.
He joins Saitama in a video game contest against the Blizzard Group. He loses after he destroys his controller. He, Bang and Saitama save fellow heroes from Jumping Spider.
Genos arrives at Saitama's Apartment with groceries to deliver a mission to Saitama. Genos responds to King's question on team heroes as a method for weaklings. When Saitama suggested they should form a team, Genos immediately praises the idea.
He appears at the end, after defeating a demon level monster.
Genos and Saitama are at the beach when Saitama asks him if he can swim. Genos explains that Dr. Kuseno made him some parts for swimming and leaves to prepare them. while relaxing in the ocean, Saitama wonders where Genos is and calls out his name. Suddenly, a periscope lifts Saitama, revealing Genos as a submarine with Saitama yelling to get a hold of himself.
After Saitama finishes his story about how he got his suit and its importance to him, Genos deduces it as Saitama telling him that in order to become a true hero, you have to have something very important to you. Genos also tells Saitama that he thinks it's about time Saitama got a new suit, and offers to gift him one, provoking Saitama to ask if Genos was even listening to what he was saying.
Genos wants to learn the secret to Saitama's power and decides to follow him and to observe everything he does, even stealing the long and soft fry Saitama was looking forward to eating. 
Saitama gives Genos a key to their apartment and they both mull over items to buy for dinner; however, upon remembering a limited time sale at two separate supermarkets, they split up. Genos then senses a monster at a nearby shopping strip and defeats it. However, this makes him miss one of the sales. Once he reaches the other (closed down) supermarket, Genos bumps into the Typhoon Family's No. 2 man and the rival C Class criminals The Pacino Family, headed by Don Pacino. Pacino mistakenly believes Genos is associated with the Typhoon Family; he steals the apartment key and kidnaps both men, promising to let them and the keys go once Genos states his case. Once Genos finds out the family are wanted criminals, Genos and the family opens fire. Genos easily defeats them and takes his key and the Typhoon Family's No. 2 man with him.
Genos is seen towards the end of the episode, having hotpot with Saitama.
Saitama and Genos are seen near the corpse of a monster they just killed. Saitama tells Genos about how cabbages can taste great when paired with barbecue sauce, which Genos interprets as being told that even the most powerful weapon would be meaningless if its wielder is weak. They are then invited by Bang, who was secretly watching, to his dojo. They initially refuse but are lured in by Bang offering them free meat. Upon reaching Bang's dojo, they are challenged to various games by Bang. Genos sits by watching Saitama play. The episode ends with Genos asking for the promised meat and rejecting Bang's offer to join his dojo.
He is on a train and receives a call that a bomb was put on the train. He, Fubuki and Swim team up to evacuate the train and stop the bomb. He attempts to stop the train and is thrown away by Tatsumaki using Telekinesis. He is later seen being repaired by Kuseno.
Child Emperor investigates the murder of Zombieman. When Saitama is put under suspicion, Genos promises that he will vouch for Saitama even if he's the culprit. 
Sonic, Becoming SaitamaEdit
Saitama and Genos split up to find and destroy a monster. Genos takes down the monster and looks for Saitama. He finds Speed-o'-Sound Sonic who was disguised as Saitama. Genos is astounded when Sonic tells Genos that he battled a monster and was hit in the head making his memory foggy. As such he forgot Genos's name. He asks where the monster disappeared to, then heads towards the mountains to search and destroy the monster.
Genos is a playable character in the video game, One Punch Man: A Hero Nobody Knows.
Genos is one of the various characters able to be summoned. His arms are bonus equipment that deal blinding damage.