"Saitama" (サイタマ, Saitama) is the sixth chapter of the One-Punch Man manga series.
The fight between Genos and Mosquito Girl begins with Genos firing a blast at Mosquito Girl who easily dodges it and throws herself down at Genos and takes out his arm and flies off with it. As she flies away, she notices that her legs are gone below the knees and looks down to see Genos tossing them onto the ground, she then sends more mosquitoes at Genos so she can fly away.
While Genos is distracted, she calls all of her mosquitoes to give her blood. Genos is about to attack the mass of mosquitoes surrounding Mosquito Girl when he hears someone yelling and turns to see Saitama running onto the street, Genos tells him to hide or he may die. At that moment all the mosquitoes swarm down towards Genos and Saitama, all of which get destroyed by Genos, creating a massive explosion and fireball. Genos then realizes about Saitama, thinking that he killed him in the explosion, but is shocked to see Saitama standing there unfazed, but completely naked.
Mosquito Girl, now more powerful, attacks Genos, ripping him almost in half at the chest. Genos then spins around and attempts to punch Mosquito Girl, but she dodges his attack easily and starts to attack him mercilessly eventually cutting off both his legs and shredding his torso in half. Genos begins to fall to the ground and decides that he will self-destruct to destroy her and is about to when Saitama slaps Mosquito Girl in the face, sending her flying through a building and into the distance, killing her and offhandedly remarking that he hates mosquitoes. Genos then asks Saitama his name and to be his disciple.