You have recently finished watching My Hero Academia and One Punch Man and you are already looking for a possible crossover and thinking that how two animes can be so similar, yet so different. My Hero Academia and One Punch Man both indeed raise your curiosity and excitement levels, both these animes are very well made and loved by many. Both these have characters that you love immensely, some characters are quirky, some are not (no pun intended), but they all leave an impression on the viewer’s mind and heart.

Both these shows have many similarities, like both of them have monsters, evil people attacking and heroes coming in to save the day, but they also have many differences like in One Punch Man, heroes are not all good and have some ulterior motives unlike My Hero Academia, where heroes are mostly pure and good and have very little to no shades of grey.
So, if you are looking for ‘what-ifs’ about My Hero Academia and One Punch Man crossover or wondering if they are in the same universe or what if they were, then I have put together few theories from the internet and also some of my own.
One Punch Man is the future of My Hero Academia
According to many what-ifs on the internet, this is among one of the most popular ones and convincing. We all know how in One Punch Man aliens and monsters are a common occurrence and also cities are not permanent in One Punch Man. Cities are named by alphabets and if a city gets destroyed people just moved to another one, it seems quite futuristic. So, according to this theory One Punch Man is setup decades in future of My Hero Academia.
One For All is getting transferred from Izuku Midoriya to other people, generation after generation and it is Saitama who gets it, when the current One For All inheritor sees Saitama saving a person heroically despite not being a hero. And just like how All Might turns into a big muscular man, Izuku turns green, just like that Saitama became bald as a manifestation of One For All. This theory is worth giving a thought.
There might be no Izuku Midoriya, at least not as we know him now
So, if we let go of the first theory and assume that they indeed are in the same time, then My Hero Academia will be totally different from now. If All Might had to transfer his quirk now, he would have 2 options infront of him. Izuku Midoriya and Saitama. Why, you must ask? Then I will say, both Deku and Saitama saved a person, despite not having any apparent superpowers or quirks, but both of them wanted to help. So, if All Might were to come across Saitama, then it was a possibility that he might give his quirk to him instead and we won’t even know who is Deku.
Izuku Midoriya will then be just another person who admires All Might. This is surely sad, but the interesting part is how amazing it would be to see Saitama have One For All as well as his innate strength and abilities. He would have become even more powerful than now. It will be disheartening to not see Midoriya but amazing too as we can now see even more powerful Saitama.
All Might will not be the strongest of all

So, in my opinions Saitama is way stronger than All Might. All Might is no joke but as compared to Saitama, he is less powerful. While not denying the fact that All Might will still be very powerful, maybe second to just Saitama. All Might in his prime was way more powerful than he currently is. While fighting Nomu he used 50-60 mighty blows while it would take only 5-6 in his prime, as stated by him, but we have seen Saitama fight even more dangerous and stronger villains than Nomu and it took him just one punch, so we can clearly see the difference here.
Saitama literally has God-Level power and his ability is beyond any human being. Saitama also has more stamina and durability, thus making him last even longer on the battlefield. One For All sure is a powerful quirk but not as powerful as you would like to think, atleast not when we compare it with Saitama.
There might be a much more powerful league/association of evil beings
Both My Hero Academia and One Punch Man have some dangerous villains/monsters. In One Punch Man the villains are aliens, monsters and different human/non-human creatures but in My Hero Academia all the villains mostly are humans but with special powers, so it differentiates them both. If My Hero Academia and One Punch Man were to take place in the same universe then we would see even more stronger and powerful villains.
This world will have worst of both, All for One and Tomura of My Hero Academia and Geryuganshoop and Carnage Kabuto of One Punch Man, thus making it very difficult for the heroes. Considering this we can also say that they will be able to influence more and more people to join them and wreak havoc on the people. They might even find a way to combine their powers and other ways to become more powerful like Shigaraki did with Nomus. So, if these worlds were to combine it will become very dangerous for heroes and civilians alike.
Structure of society, heroes and villains would change
We know by now that the world of My Hero Academia and One Punch Man are quite different. One Punch Man having temporary cities while My Hero Academia having permanent ones, like we do. The ranking system of heroes is also different in both the animes and so is the society of heroes. In One Punch Man the heroes are rated on how they ‘appear’ to the general public and not entirely on their strength, its biggest proof is Saitama being C class and later being promoted to just B class on the other hand in My Hero Academia the heroes are rated mostly on the basis of their strength level. One might argue that Endeavour was not given the most powerful hero tag because of his lackluster and rather rude public appearances, but we all know All Might is powerful than him, even he accepted that. Also, in My Hero Academia, the League of Villains is more organized and efficient than Monster Association in One Punch Man.
So, if both these animes were to take place in the same universe than a lot of things would change. We would see more anti-heroes like ‘Hero Killer Stain’, who don’t like the commercialization and glamourization of heroes, especially now when One Punch Man has so much of it. The League of Villains and Monster Association might have a power battle between the top brass, which would be amazing to watch, or it might become even more dangerous if they combine their forces. The society overall will change, having some features of One Punch Man and some of My Hero Academia, it will be a hybrid of both.
Saitama will teach Bakugo

So, hear me out! Let’s suppose All Might did give his One For All to Deku and Saitama is just another hero, powerful than All Might, but since he has low rank, he has to teach kids at UA High and train them about quirks. But he also kind of likes it. Without a doubt he will take interest in Bakugo and I also think that Bakugo will also consider him his idol, as we know Bakugo doesn’t care about what is shown in news or what people think, he will realize that Saitama indeed is more powerful than All Might. Now can you imagine how fun it would be to see Saitama training a brat like Bakugo. Bakugo who doesn’t care about anyone and is literally a brat, getting taught by Saitama.
All Might and other teachers can be considered soft in front of Saitama who will just beat Bakugo, not caring about where he hurt him. It will sure be fun to watch their banter and short-lived battles, but training with Saitama is definitely going to make him much stronger. (Naruto reference) It will be like Kakashi training young Team 7. Their dynamics is what I would like to see and I think everyone would enjoy it.
So, that’s all I can think of if One Punch Man and My Hero Academia were to take place in the same universe. If you have some more theories and ideas then let me know in the comment section. Also check out: