The Five Killers was supposed to be an original creation from writer/producer Eric Calderon as an animated TV series (12 episodes with a 1 hour finale) done by Gonzo. The designs were created by manga artist Maeshima Shigeki and the trailer was done under the direction of Trinity Blood director Hirata Tomohiro. The trailer is unfortunately all that came out of this project due to GDH's alarming financial situation.

[Source: AniDB]