Simon, a shy and naïve young man, and his charismatic friend Kamina live underground in a small village beneath a world of earthquakes and cave‑ins. Kamina is convinced that a surface world exists above their heads, while Simon has yet to realize his own destiny. Their lives change when an earthquake collapses the village’s ceiling, and a gigantic Gunmen arrives from the surface along with Yoko, a beautiful girl armed with a superconductive rifle. Together, Simon, Kamina, and Yoko pilot the mecha Lagann, which Simon uncovers from the ground, and they fly toward the surface, beginning their battle against the Beast King and the secrets that lie above.