Kekkai Sensen

Three years ago, a gateway between Earth and the "Beyond" opened over the city of New York. In one terrible night, New York was destroyed and rebuilt, trapping New Yorkers and extra-dimensional creatures alike in an unassailable island, a world all its own hidden in the mist of its physics-defying waterfalls.
New York has been rechristened Hellsalem's Lot, a paranormal melting pot where magic and madness dwell alongside the mundane, where every form of human vermin gathers to exploit otherworldly assets for earthly profit. Now someone is threatening to breach the controlled flow of harmless, average humans and items in and (much more rarely) out of the city and thereby release Hellsalem's Lot's deluge of horrors on the outside world. The mysterious super-agents of "Libra" fight the impossible to prevent the unthinkable.