The year is R.C. 1014. The Capital Tower, an orbital elevator, connects earth and space. Due to its role in supplying Earth's power by transferring Photon Batteries from space, it is worshiped with a religious fervor. Bellri Zenam, a cadet in the Capital Guard formed to protect Capital Tower, is participating in his first non-simulated exercise when he is attacked by the powerful but unaffiliated "G-Self" mobile suit.

It is now the year 2577 and the first manned ship to Mars has landed on the planet and the six crew members are ready for their mission. But what they find are giant mutated humanoid cockroaches with incredible physical strength.

A gate to another dimension has burst open, and from it emerge gigantic invincible creatures that threaten all of humanity. Earth's only defense is a mysterious group of warriors who have co-opted the alien technology in order to fight back!