The Blizzard Group Arc is the eleventh arc of the series, and the second arc of the Human Monster Saga.
Three Figures enter the isolated area in Z-City. They are revealed to be the three top three ranked B-Class heroes Fubuki, Eyelashes and Mountain Ape respectively, who are moving toward their "target."
Meanwhile at Saitama's house, Genos reveals that the two have been promoted to B-Class Rank 7 (Saitama) and S-Class Rank 14 (Genos), and although Saitama neglected to report his work, it was still reported by eyewitnesses, which causes Genos to believe his master is finally being recognized. Genos senses an object coming in at an abnormal speed and rushes outside, trying not to disturb Saitama. The object is revealed to be Speed-o'-Sound Sonic who recognizes Genos from their previous meeting. Sonic then claims he came to battle Saitama as his rival, which angers Genos, causing both to prompt each other into a fight. At the same time Saitama overwrites a save data on King's handheld gaming console which he took from King's apartment.
20 minutes later, the three B-Class hero are outside Saitama's door, with Eyelashes yelling at him to come out. Blizzard of Hell introduces herself to Saitama, but Saitama is not impressed. She then tells him of of the factions in the Hero Association and threatens him to work under her. Saitama refuses, which causes both Eyelashes and Mountain Ape to attack him, but the two are then swiftly defeated
After Saitama defeated her subordinates, Fubuki uses her psychic powers, but Saitama is not surprised by her abilities. She uses a technique called Hell Storm, which leaves her opponents bone cracked and flesh ripped apart, but Saitama managed to get behind her and patronized her on being a hero. Fubuki was angered by his statement and use a barrage of different techniques, all of which were ineffective against Saitama. She tearfully attacks Saitama with a box cutter but was caught up in Genos' and Sonic's attack. She managed to evade the attack, only because Saitama came in between the explosion. She meets Genos and was surprised at the fact he was Saitama's disciple. Sonic threw an Exploding Shuriken at Genos, but the attack was ineffective.
Sonic comes down from atop the street light, boasting that he shall beat Genos and Saitama shall be next. Meanwhile, Fubuki notices his killing intent and claims him to be dangerous. Genos tells Saitama that he shall beat Sonic, to which Sonic is amused as he claims Genos to be slow. Genos then responds that he did not show what he is truly capable of. Genos then accelerates himself and quickly moves behind Sonic, unsuccessfully attacking yet again because Sonic manages to catch on and dodge. Saitama and Fubuki witness the match and while Saitama notices Genos moving faster than he did when they fought, even hypothesizing that he got new parts, Fubuki is unable to keep up with the speed of the two.
After a bit of fighting, Sonic notices Genos keeps getting behind him, thinking he is mocking his speed. Genos then drops Sonic's topknot, leaving him with short hair, which angers Sonic.
Genos gets behind Sonic and attacks with his Machine Gun Blow technique, only to be surprised to learn he had only hit an afterimage. Sonic then retaliates with his secret technique: Four Shadows Burial - Scattered Flash Slash, which Genos cannot follow. This prompts Genos to blow up the entire area, going at maximum power. Afterwards as Sonic is thought to have beaten Genos, he realizes Genos had fallen before he was able to cut him. Learning Saitama was responsible, he calls him soft for wanting to protect his pupil, to which Saitama replies it was to prevent Genos from destroying the place, since they live in the vicinity. Saitama then tells Genos to stop his fight as for he himself was Sonic's target, then states he shall take Sonic on seriously. Sonic then states he shall use his ultimate technique he developed, in order to kill Saitama.
Meanwhile, Fubuki is watching the entire fight, and is glad she's ignored for otherwise she might have been in danger.
Sonic attacks Saitama with his ultimate technique: Ten Shadows Burial, to which both Genos and Fubuki are impressed but are still capable of seeing. He does not have the upper hand and Saitama counters with his own super move: Serious Series - Serious Side Hops, creating an infinite amount of clones and beating Sonic. Sonic then appears to be knocked out, which to Genos resembles death, but Sonic managed to instantly leave. Fubuki, seeing everything, claims Saitama to be too strong.
Fubuki explains the reason why she stays in B Class is because she will never reach the top of the ranks like her sister Tatsumaki. As such, when she became B Class she took control the lower heroes in order to surpass her sister, who is a lone wolf. Genos comments she could be at the top of A Class, but Fubuki states that it is impossible, because she will never be Rank 1. She explains that Atomic Samurai's three disciples Bushidrill, Okamaitachi and Iaian are unable to get to S Class, because of Sweet Mask, who is securing Rank 1.
Meanwhile Suppon, a caveman escaped from a nearby lab, is causing havoc on the streets and Sweet Mask was ordered to bring it back alive. The caveman hisses at him, but Sweet Mask comments he isn't that sweet.
Suppon attacks Sweet Mask, but he easily dodges and counter attacks the caveman, killing him instantly, with the crowd cheering for him. At Saitama's apartment, Fubuki tells Saitama that he might be a monster himself, but nowhere near Sweet Mask or Tatsumaki.
Fubuki tries to justify her action, though Saitama has nothing against it; he doesn't feel like being her henchman. Moments later, much to Fubuki's shock and awe, King arrives, asking for his game. Saitama returns the game, admitting he accidentally erased King's data. Fubuki, surprised at how S Class heroes are attracted by Saitama's strength, begins thinking about joining the others.
At the Hero Association meeting, Saitama and Genos are given hero names. Genos is named Demon Cyborg, while Saitama is simply named Caped Baldy. Sitch is furious over the meeting, debating names rather than about Garou's rampage. They explained Bang volunteered to get rid of Garou and there is King, Tatsumaki and Blast if all else fails.
Meanwhile Garou coincidentally, ran into Tanktop Vegetarian, and defeats him, but was not satisfied by the fight. He happily announces his hero hunt and couldn't wait to fight monster class heroes.