Orga's team has been hand picked to escort Kudelia, the young leader of the Martian independence movement, to Earth for an important meeting. Just as preparations for departure are underway, Gjallarhorn attacks the base in an attempt on Kudelia's life.
The adults of CGS flee in the face of Gjallarhorn's attack, using Mikazuki and the other children as decoys. Gathering the children who have been left behind, Orga decides to fight back against Gjallarhorn, and puts a certain plan into motion.
Thanks to Mikazuki and the Gundam Barbatos, Orga's group has temporarily repulsed Gjallarhorn, though not without many sacrifices. As they are discussing their next move, one of Gjallarhorn's Graze mobile suits again appears at the CGS base.
Kudelia is distressed that so many boys have lost their lives because of her. Mikazuki takes her to the farm run by Biscuit's grandmother, where an unexpected encounter awaits.
Kudelia and Tekkadan finally leave Mars behind them and head for Earth. With a ship waiting for them, they attempt to travel by shuttle to a low-orbital station, but are attacked by Coral's Gjallarhorn forces.
The members of Tekkadan need a guide in order to reach Earth despite Gjallarhorn's surveillance. To gain a powerful backer, they attempt to negotiate with Teiwaz, which is based in the Jupiter Sphere.
Tekkadan has made contact with Turbines, which runs Teiwaz's transport division. But they find themselves clashing with Turbines over their group's origins and property.
Having demonstrated Tekkadan's strength and legitimacy to Naze, the leader of Turbines, Orga and the others renew their negotiations with Teiwaz. Meanwhile Atra visits Turbines's warship, bringing the frustrated Kudelia with her.
Accompanied by Naze, Tekkadan visits the Saisei, the stronghold of Teiwaz, in order to meet with Teiwaz's representative McMurdo Barriston. Here, Orga receives a surprising proposal from Naze.
Tekkadan and Turbines go on ahead to Earth, leaving Mikazuki and Yukinojo on the Saisei to complete final adjustments to the Barbatos. But the events aboard the Saisei have greatly affected their respective states of mind.
While on patrol, Akihiro and Takaki encounter unknown enemies and engage them in battle. The attackers turn out to be Brewers, a pirate group that operates between Mars and Earth.
Mikazuki and Orga learn that Akihiro's long-lost younger brother is one of the Brewers mobile suit pilots. Tekkadan challenges Brewers in order to get back Akihiro's brother.