Chapter Text
First important thing to know is that in this universe abilities and quiks DO NOT affect one another.
They are fundamentally different. The origin of abilities and their nature is unknown and mysterious, while quirks are genetic and they have been studied to the point where they have little to no secrets.
This is, of course, why No Longer Human had an effect on Elise but not on Bakugou's explosions and on the swamp Villain.
In this Universe, Yokohama is a closed off city for the public. It was a choice made to avoid for abilities and quiks to come in close contact, and so avoid causing chaos due to the difference between the powers, as they would be too hard to handle simultaneously.
Abilities existed for a lot more than quirks, but they have never been of common knowledge to people due to how rare they are. But the government is well aware of them. So the moment it was clear the people born with powers weren't ability users, they put in action a plan to avoid more commotion than necessary.
Yokahama was chosen to be the 'world of ability users' by the Japanese government since it had the lowest number of newborns with quirk. These people, along with their family, were brought out of the city, while people with abilities were brought in.
Until Yokohama was devoid of quirks, and the rest of Japan was devoid of abilities.
Of course afterwards there were other cases of quirks in Yokohama, but after bringing them out, a few years later there were no more signs of quirks.
It wasn't that easy for abilities, since they are granted without an (apparent) logic. And the HPSC still keeps a close eye on the newborns for anything out of place.
Yokohama is still under the Japanese government.
(The Hunting Dogs still operate within the military of Japan, and do work outside of Yokohama, but they are known by the public only in the city. They still have the political influence and importance they have in the show, it is just not extended to the public.)
The Special Division for Unusual Powers (SDUP) and the HPSC work together to keep an eye on possible ability users born outside the city of Yokohama, and work a way to get them in the city.
The Port Mafia also likes to keep an eye on the possible ability users in the rest of Japan (It's actually just Mori), even though they are not supposed to.
The SDUP lets them, since most of the time it's impossible to bring the person to Yokohama in a clean and legal way. So if they can let the criminals do the dirty work they will.
The HPSC is not that happy about this, mainly because they don't want the PM to gain influence in the rest of Japan, but they have no say in this since there is no actual proof of the PM exiting Yokohama to do so.
In the future, when the PM will gain the licence to legally use their abilities, they will also gain the legal permission to go outside Yokohama and bring ability users inside the city.
The heroes are all told to not interfere with Yokohama by the HPSC. And only the top heroes, and underground heroes, are allowed to have access to actual information about the city, and even then, it's not much.
To the rest of Japan, Yokohama is a closed off city without any information about it to be found anywhere.
Of course this means that humors will rise, the most typical ones being that It's quirkless city or that It's ruled by Villains (the typical rumos of every fic basically) but since there is absolutely NO official information, the people lose interest or get tired easily, since there are no developments to follow aside from the occasional conspiracy theory about the city.
And that is technically all you need to know about this AU! You are free to use this (or pieces of this) in your own fanfic if it inspires you, just make sure to give me credit pls 🙏
Thank you so much <3
If there are any questions feel free to ask them!