Knight Hunters OVA

Overview

Someone out there is determined to see the fall of Weiss Kreuz, and it looks like they have found the perfect plan for it. The four assassins find themselves trapped in a deadly game of deceit, where the question of honor versus duty comes to surface. Now they must fight for their own reasons to survive--and there can be only be one victor in this field of death. (Source: AniDB)

Source: AniList