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 extradimentional creatures alike in an impenetrable bubble. Now, 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 otherwordly assets for earthly profit. Now someone is threatening to breach the bubble and release Hellsalem's Lot's horrors, but the mysterious superagents of Libra fight to prevent the unthinkable.
Libra's members operate both inside and outside the city and are typically blood-technique users or some description of super-human. The full scope of the organisation is unknown and, due to its secretive nature, precise information regarding the organisation is said to be worth billions to the criminal underworld. Law-enforcement agencies within Hellsalem's Lot also appear to be after Libra, probably due to their vigilante activities. However, the police have been shown to co-operate with Libra in severe circumstances to achieve a common goal.
With the branch of Libra operating in the Hellsalem's Lot lacking in new members due to transfers being needed across the hot spots in other areas new, and older members are reinstated in order to help combat the everyday evil King, and Queen of Depravity.
===
Rather simple premise, and there's not much to say otherwise. If someone has questions please ask below. There is a wiki, beware of spoilers, for this anime if you need any questions answered about what it is.