Turbulence in time and space caused countless universes to collide, bringing the protagonists, villains, supporting characters, and even background characters from many works into this vast and bustling city. A being who called itself the city's administrator welcomed them and explained that they could complete missions in the city to earn points. Once space-time stabilized, they could spend those points to make their wishes come true. With enough points, you could fulfill any wish, even rewrite the course of a story.
Every character summoned to the city received a "balancing" adjustment, bringing their powers closer together. So whether they came from a high-magic world or a martial arts world, their strength in the city was roughly the same.
In short, gods, demons, heroes, and ordinary people all clash in a massive battle across the city.
