2016, a year and a half after the assassination of Princess Asseylum. Slaine, who has earned the status of Mars Knight in spite of being an Earthborn is now served by his own personal subordinate and has been taking part in battles against the UEF. Elsewhere, the Deucalion is finishing up repairs in order to proceed to a new battlefront. One after another, the ship’s former crew returns.

At the Vers Empire’s frontline stronghold in Earthspace, Slaine leaves for their base on Marineros Island accompanied by the Stygis Squadron, compound Kataphraktoi. Meanwhile, the Deucalion arrives at the United Forces of Earth’s Trident Base, but some of the soldiers there are not fond of a unit that is equipped with Aldnoah.

Lt. Marito, who is serving with Yuki Kaizuka, receives orders for a new operation. Yagarai is concerned about the position this will put Yuki in, who has been assigned to a unit away from the Deucalion. Meanwhile, a group of Mars Knights who oppose the Earthborn Slaine’s rise to power plan a new attack on Earth in hopes of securing more power of their own.

Irritated by Slaine’s actions, Count Marylcian works out a new strategy with Count Barouhcruz. Elsewhere, Rayet loses her composure in front of the Mars Knight prisoner, and Inaho deduces her true intentions. Meanwhile, Slaine talks about birds with Eddelrittuo.

The UFE is overwhelmed by the Mars Knights’ advance. Inaho and the Deucalion take part in the fighting, but they find themselves hard pressed by an unexpected attack. Elsewhere, Slaine unburdens himself to Eddelrittuo. A Mars Knight who requested an audience with Princess Asseylum did so with an ulterior motive.

Inaho and the crew of the Deucalion steel themselves for the final battle. Capt. Magbaredge confronts Vice Admiral Hakkinen and takes part in the dangerous mission. Meanwhile, Slaine is determined to commit all his forces to prepare for a final showdown. Princess Asseylum, having been rescued, resolves to confront their fate.

The war has come to one final battle. Having reached an understanding, Slaine resigns himself to his fate. Elsewhere, Inaho answers the call of his own destiny. There is someone who sheds tears at the sight of the battlefield where all too many lights flare, then die out. A solitary girl saw the final moments of their battle.