After defeating Face Ripper and several other monsters beforehand, Genos heads for the final monster invading C-City. When he arrives at the site, he sees a few defeated heroes on the ground. Genos immediately goes to one of these heroes and asks him if he's alright. The hero informs Genos of what kind of mysterious being it is and to never take his eyes off the monster. Awakened Cockroach speaks from behind, recognizing Genos as an S-Class hero and asks the hero if he also despises cockroaches. Genos observes the monster, finding his nature as an insect quite fitting and prepares to swiftly eliminate the monster in order to make it to Saitama's match in time. However, he reminds himself not to be overconfident and stay on-guard against such an opponent, for he's already learned that lesson the hard way. The two fighters quickly begin their battle.
Genos launches himself at Awakened Cockroach and throws a right uppercut, which the monster dodges. He strikes with a flame-powered punch that is again avoided, the force of the punch burning several buildings in front of him. The two engage in a quick exchange of blows. Awakened Cockroach punches Genos across the face, performs a backflip several meters into the air, and hides behind an alleyway.
Awakened Cockroach mocks the teenage hero and lands a string of punches which throw Genos to the ground. The cyborg quickly gets back on his feet, but by the time he does, Awakened Cockroach has already disappeared. Genos realizes that he cannot read the monster's movements due to his nimble footwork in addition to his expert usage of the buildings to create dead angles. Even if he destroys the entire area, Awakened Cockroach can simply jump mid-air, and the smoke that would be created would allow Awakened Cockroach to land several surprise attacks.
Left with no other options, he regrettably prepares to use a secret weapon. Awakened Cockroach's interest is piqued, and he asks the hero what this weapon could be. He also tells Genos in advance that even if he could attack at the speed of light, his senses would sense killing intent and dodge on its own. Genos also comes to the conclusion that he must accept that there are monsters in the world who surpass him in certain fields.
Awakened Cockroach jumps to the top of a building, and comes to a decision: he will damage Genos beyond repair and allow other monsters to finish him off. Awakened Cockroach bids farewell to Genos, jumping off the building and going behind Genos. However, as he prepares to strike Genos from behind, in a shocking turn of events, Awakened Cockroach is immobilized. The monster looks down and realizes there is some liquid substance on the ground. Genos informs Awakened Cockroach that this is an extra strong instant adhesive designed to deal with speedy opponents like Speed-o'-Sound Sonic. He also expresses frustration for being forced to use this, since it means admitting his own speed wasn't enough to deal with Awakened Cockroach.
The monster asks Genos what he's talking about, and Genos replies that it's none of his business. Genos prepares an incineration blast, engulfing the street in smoke and flames. When the smoke clears, Genos realizes that Awakened Cockroach sacrificed the bottom of his legs to escape, but knows that he's been dealt significant damage and there is no use pursuing him. With the battle finished, he prepares to go back to the stadium to watch Saitama's match.
As Genos is walking back, he picks up on high-speed movements approaching him. He wonders if it's Awakened Cockroach, but realizes it's something else entirely. Indeed, the monster is Gouketsu, an executive of the Monster Association who's on his way to the C-City Super Stadium, and defeats Genos with a single blow.
When the monsters return to the Monster Association, Awakened Cockroach is called out for his defeat against Genos by Gyoro Gyoro and Orochi. Orochi impales the monster with his horns at speeds Awakened Cockroach isn't able to naturally react to, despite his claim that his body could react to light-speed attacks. He pathetically asks for assistance as he's consumed by the Monster King and the other monsters watch his death.