The future. The people that migrated to an alternate dimensional space, seeking a new world to live in, started an armed rebellion in order to declare independence from Earth. Thus, multi-dimensional war broke out with the United Army of Earth. The battlefronts spread, and the fight grew long.

In their desire to break the deadlock, the United Army of Earth decided to launch a large-scale offensive, deploying to the front line vast amounts of "Assault Girls" -- new arms that would render all previous weaponry ineffective. Piloted by outcasts and criminals, the members of the The 13th Independent Assault Girl Hunting Platoon -- dubbed "The Hyena Platoon" -- are tasked with hunting down and destroying rogue Assault Girl pilots, who have succumbed to the corruption that eventually befalls all pilots.