Antengai: Twilight Metropolis

The manga centers on the titular Antengai, a city in a solitary island, unclaimed by any nation, calling no land its sovereign, and cut off to the outside world. Here, humans and ayakashi beings exist in a lawless urban sprawl. The manga follows the various stories of the denizens of Antengai, as they try to extract the truth of a city that hides it from them, and what price they would be willing to pay to get it.

(Source: Anime News Network)