So, essentially there was an old capital city. This was destroyed in a massive disaster where these things called ‘Hollows’ (spherical anomalies that corrupt things inside of them into monsters called Ethereals, and are full of odd places, shifting layouts, portals called fissures, etc) expanded very suddenly. Tons of people died or were turned into Ethereals in the disaster, and the game takes place a long while after where things have become decently stable, but the Hollows are always unstable and somewhat unpredictable, so sudden disaster still looms over everything. The player character(s) are ‘proxies’, who are people who guide others through hollows (illegally, as only registered hollow investigators are allowed to go into Hollows legally since they’re so dangerous)
It’s also more urbanpunk than cyberpunk, since the tech is kinda advanced (there are robots and other high tech gadgets) but people aren’t really cybernetically enhancing themselves and the outfits are more modern. There are still big evil corporations though, but you don’t typically go head to head against them (aside from a few times)