300 years after the Calamity War's end.

The powers which ruled the Earth Sphere have been overthrown, giving way to new rulers of a new world, exhausted of battle. Meanwhile, far away on Mars, the sparks which threaten to ignite a new war have been struck...

Our protagonist Mikazuki Augus, a member of the private security firm Chryse Guard Security (CGS), takes on a mission as bodyguard of Kudelia Aina Bernstein, a young girl who agitates for Chryse's independence from Earth. However, when the elite Gjallarhorn unit, charged with suppressing revolutionaries, raids CGS, its higher-ups deliberately use Mikazuki and the other boys as a decoy to cover their own retreat. Orga Itsuka, leader of the boys' squad, takes this abandonment by the adults as motivation to launch a full-fledged coup d'état. With orders from Orga to hold back Gjallarhorn, Mikazuki sorties in Calamity War-era scrap that CGS had been using as a generator—the Gundam Barbatos...

[Source: Gundam.info]

The second season of Mobile Suit Gundam: Iron-Blooded Orphans.

Year P.D. 323. Gjallarhorn's political intervention into the Arbrau central parliament escalated into an armed conflict using mobile suits. The incident was brought to an end by Tekkadan, a group of boys who came from Mars.

News of Tekkadan's exploits has also reached the ears of Wistario Afam, a youth born and raised at the Radonitsa Colony near Venus. Venus, which lost to Mars in the contest for development, is a remote frontier planet in which the four great economic blocs show little interest. It is now used only as a penal colony for criminals, whose inhabitants don't even have IDs.

Then Wistario, who hopes to change the status quo of this homeland, encounters a girl who claims to be the guide to the Urdr-Hunt.

[Source: Gundam Global Portal]