Mankind expands into the depths of space in a search for new land. The terraformed Mars is home to colonies from various Earth countries, and mankind's push continues on to Jupiter. However, with new resources and new territory come new problems. Mars consists of 16 counties, which are equivalent to the "states comprising many Earth nations. Martians and the colonists of the Jovian system are ruled by Earth with an iron fist. Such people living on the frontier of civilization are called "Enders". An irreparable rift forms between those bound by the chains of Earth's gravity and those floating free in space, and over time the hostility between the governors and the governed grows.
In the course of exploring space, man discovers a new ore called Metatron. It gains attention not only for its use as an energy source but also for a multitude of other purposes. However, the incredible energy it provides also comes to be used for military designs, as anti-Earth forces on Mars employ it to secretly develop the giant humanoid weapons known as Orbital Frames. The Orbital Frames possess overwhelming mobility compared to Earth's LEVs, similar humanoid weapons. Once unable to compete against Earth's sheer numbers, Martian anti-Earth forces finally have a weapon with which they can fight back.