Manga by author Nightow Yasuhiro - Status ongoing

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, rebuilt, and rechristened Jerusalem's Lot, a paranormal melting pot where magic and madness dwell alongside the mundane. The mysterious super-agents of Libra fight the impossible to prevent the unthinkable.

Vash the Stampede is a gunman on the run with a 60 billion double dollar bounty on his head which has made it difficult for him to go anywhere without being chased and shot at. Because of the bounty, every town he ever visit ends up being destroyed because of his pursuers, and miracliously, no one ever gets killed. Meryl and Milly are two insurance agents that have been sent to find Vash the Stampede and keep him under surveillance so no more damage is caused. Meryl, who leads the pair, can't believe that the man they have met can possibly be the legendary gunman. This spikey haired, gangly, and blonde young man is extremely friendly, a pacifist, hates blood and suicide, absolutely loves donuts, and is a dork and a crybaby...there is no way he could he be Vash the Stampede, a notorious outlaw. However, there's more to Vash than just smiles and dounuts.

From Dark Horse: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 Jerusalem'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 unharmful, average humans and items in and (much more rarely) out of the city and thereby release Jerusalem's Lot's deluge of horrors on The Outside. The mysterious super-agents of Libra fight the impossible to prevent the unthinkable.Each volume has a subtitle:Vol. 1 (Mafuugai Kessha) Secret Society in the Sealed City of MagicVol. 2 (Sekai to Sekai no Game) A Game Between WorldsVol. 3 (Shingeki no Blood Hammer) The Tremorous Blood HammerVol. 4 (Kenkaku no Eden) A No-Holds-Barred E-denVol. 5 (Z no Ichiban Nagai Hi) Z's Longest DayVol. 6 (Jinrou Daisakusen) Chain: PossibleVol. 7 (Macro no Kesshiken) Desperate Night in the Macro ZoneVol. 8 (Maboroshi Byoutou Rises) The Phantom Hospital RisesVol. 9 (Erakokyuu Blues) Branchial Respiration BluesVol. 10 (Yougan Genshikou)Japanese manga and anime site: http://kekkaisensen.com/