In the latest update on NIS America’s Prinny Bomb post, the North American release date has been revealed, along with the NISA-exclusive premium edition. This edition of the game, only available on the publishers online store, as with most of their titles’ limited editions, contains the game, a hardcover art book, a poster featuring Syrma’s awakening, along with a zodiac keychain.
The release date for both the limited edition and standard edition is listed as May 20th on the site, but no confirmed details on the European release date have appeared so far. However, after a quick look on Amazon and ShopTo, they both have the UK release marked as May 16th, the Friday just before the American launch date, or May 9th, which is the Friday before that. Hopefully an official European launch date will be confirmed soon by NISA, but with their recent track record on most of their releases (other than Atlus titles) they have been pretty good at getting the European versions out within a week or two of the North American releases.
You can find both the premium and regular editions on the NIS America Online Store, containing a copy North American version of the game.