The entire year is post-disaster 323. More than 300 years after a wonderful war between Earth and Mars referred to as the"Calamity War", Mars has been successfully terraformed and colonized by humans. Yet despite the technological advances, the humans on Mars crave freedom and also try to improve their livelihoods. Furthermore, while almost all of Mars' states have received independence, the planet is virtually reliant on Earth for improvement. A new orphan named Mikazuki Augus is part of a set of children who work with its civilian security company Chryse Guard Security, entrusted with the safety of this Martian Princess Kudelia Aina Bernstein, who's plans for her nation of Chryse to safeguard independence from Earth. 1 afternoon, the band was assaulted by the Earth Military organization Gjallarhorn, which intends to avoid the Martian independence movement. Throughout the attack, the leader of their children and the Third Army Division within CGS, Orga Itsuka, determines to rebel against the adults along with higher ups who had escaped and abandoned the children and foot-soldiers to remain and struggle since decoys. Augus must choose to either follow his assignment his friends since he glanced to the legendary mobile lawsuit: the Gundam Barbatos.