Gate Keepers

Arsenal Girls are not natural but are summoned into the world as a natural counter to the Invaders. In the old days Arsenal Girls appeared when needed like angels on the battlefield. During the era of The Earth Sphere War a special breed of Alt Human was born. Capable of directly summoning Arsenal Girls using their psychic capabilities. When summoned the new Arsenal Girl is linked to the Gate Keeper with most powerful Gate Keepers capable of binding more Arsenal Girls. When one has a full team of Arsenal Girls they become known as Commanders.