In my opinion, and this is entirely speculation, based on Blast's conversation with Tatsumaki and his appearance, I'm going with the presumption that Saitama and Blast are related in some way or another. Blast shares the same mindset as Saitama in that they're heroes for a hobby and not for anything grand like ideals, or traumatic or happy past experiences that typically define heroes. Their costumes are both bland, Saitama's much more so than Blast's and they both have capes. If you noticed, none of the other S-Class heroes have capes so capes are unique to Saitama and Blast (excluding all other characters of insignificance). They both have enough power that it acts like a strange charisma. In Saitama's case, he has many followers and Blast, from the glimpse we've seen of him, attracted anti-social Tatsumaki to the idea of being a hero. These are just some clues that I've gathered from my perspective so feel free to interject. Note: See end before writing scathing replies about the date of these posts I responded to.
@Godon "Blast being evil might not be a threat to saitama since saitama is said to have broken the hero hero testing records physically. Hence saitama should be stronger than blast which might also not be the case.
Also with this naming sense they have got to have something in common : silver fang (bang) ,his brother (bomb), and of cause there's blast. Since those two are on top in the martial arts world, i think blast has got to be related to the martial arts world or to bang somehow. Probably."
Your first statement is not valid. Like King, Blast may have been approached by the Heroes Association and automatically installed into S-Class without taking the Hero Exams, both physical and mental. If so, he wouldn't have been able to break the record. There is a number of variables which could explain Blast not having to take the Hero Exam as well. Also, about the naming schemes you pointed out, it is an interesting connection you made. However, I don't think it plays a part in helping identifying Blast's true identity. You could be right and I could be wrong, but it doesn't seem likely that Blast is a part of the martial arts world. First, he doesn't hold himself like a martial arts master. All martial arts masters are extremely disciplined and that is what makes them masters of their crafts. From what we've seen, Blast has no discipline at all. Secondly, from what I've gathered, Bang and Bomb are their original names and have no relation to their fighting styles, instead of nicknames that were given to them based on their fighting styles. Also, if Blast was part of the martial arts community, he would be known without a doubt. The martial arts community is a very close-knit community and martial arts techniques are readily apparent to a trained eye. So, had blast ever defeated a monster or human, a martial arts master would have been able to analyze the techniques used, come to the conclusion that they don't or do recognize the style, and might possible be able to point out the user.
@syLph "Judging by his name alone I'd expect Blast to be either a master of pyrokinesis or also some kind of cyborg using weapons to blast stuff away. As for the later I could imagine him to be the cyborg who destroyed Genos hometown... like during his job because he's just overkill. That would add some fuel into the story actually, but I don't really think he's that cyborg. I guess the pyrokinesis one is more probable since we already have a couple cyborgs and someone focussing on using fire is still missing."
I could entirely be trying to think outside the box too much, but it seems highly unlikely that Blast is a master of pyrokinesis or an explosive ordinance master simply because his name is what it is. Just like Bang doesn't use guns or Bomb doesn't throw sticks of dynamite, Blast will likely not use something that is explosive, be it a power or a tool. Also, speaking after Ch. 106 (v3) was released, it is highly unlikely that he is a pyrokinetic, a cyborg, or an esper. If he was a pyrokinetic, that monster would be crispy and there wouldn't be a pool of blood beneath it. He doesn't possess an analytical mind similar to Geno's either from what I gathered from the conversation between him and Tatsumaki so cyborg seems less likely. Although it could be that all of his body with the exception of his head is robotic, but if that were true, would he really be wearing gloves or such a stuffy outfit? After all, Geno's body needs to breath so it would be within reason that Blast's body would need to as well. An esper is the most unlikely considering Tatsumaki is an extremely powerful esper and she witnessed Blast firsthand and said nothing about him being a more powerful esper. On top of which, what kind of esper wears a hero costume with gloves and all? Espers do not dirty their own hands so what is the point in wearing gloves. Just compare Blast's appearance to Tatsumaki's appearance. It's a world of difference and I don't think it is all due to personal tastes.
I realize these comments are old so put down the stones and hear me out. Even though these comments are old, they likely still reflect a portion, even if it is a small portion, of some of the readers' beliefs or views. So, I decided to put forth my views so that they may help to illuminate the dark nether regions of your brain.