Weiss Kreuz is about four young men (Ran "Aya" Fujimiya, Omi Tsukiyono, Ken Hidaka, & Yohji Koudo) who work at the "Koneko no sumu ie"
flowershop. Though the flowershop is just a cover. In reality, they are Weiss, a top secret group of assassins, charged with bringing to justice the criminals the law can't touch. Weiss Kreuz: An Assassin and White Shaman, is a prequeal to the original anime, explaining how Aya first became a part of Weiss.