Knight Hunters is about four assassins who work during the day in a flower shop. The four are members of a group known as Weiss, and take their orders from a mysterious man called Persia. They each use their own specific talent for killing to take out drug kingpins and terrorists. The main nemesis of Weiss is an enemy assassin squad called Schwartz. Each member of Schwartz also has a specific skill, but theirs are metaphysical abilities, rather than learned skills.