Weiß Kreuz (ヴァイスクロイツ, Vaisu Kuroitsu?, lit. German for "White Cross") is an anime about four assassins that work in a flower shop called "The House of Kittens", a reference to their feline codenames. The assassins are members of a group called Weiß (white), which is run by Persia of the mysterious Kritiker organization.

In addition to the two seasons of anime and one OVA series, the Weiß Kreuz franchise also includes a light novel, two manga series, and several drama CDs. Media Blasters released the anime in the North America as Knight Hunters: Weiß Kreuz.

Source: Wikipedia