Space Era Year 430. Mankind is at war with monsters of unknown origin. Throughout the front lines, mankind's forces are pushed back by the one-digit Type monsters, whose shields are impenetrable by conventional means. To deal with this, mankind creates the AB swords, which can cut through anything with ease. Only those with great potentials are able to wield these weapons. Instead of simply being called "Elite Units", they are given another name, one thats reflects their similarities with popular medieval figures. They are "Knights".