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.
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.
Under orders from United Forces of Earth’s General Headquarters, the Deucalion and her crew take part in an assault mission. They formulate a plan that will let them fight the Mars Knights. Elsewhere, with fresh determination, Slaine advances his invasion of the surface to broaden his power base. However, there are those who have doubts about his true motives.
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.
The Orbital Knights rally under Princess Asseylum’s new proclamation with renewed determination. Slaine launches a new operation, partly to contain the factions who are against him. Elsewhere, Capt. Magbaredge, who has been summoned by senior UFE officials, realizes just what they think of the Deucalion. There, she receives orders for a new mission.
Princess Lemrina is distraught over an unexpected situation, but Slaine tells her that on the contrary, he will use it to his advantage. But deep down, he gradually feels more and more cornered. Elsewhere, the Deucalion’s crew links up with a UFE company that is engaging a powerful enemy. Then, on the front line, Inaho gets out of his Kataphraktos.
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.
The Mars Knights have assembled at Marineros Island. Slaine tries to take part in the battle, but he is looked down upon by his erstwhile fellow knights because he was born on Earth. Elsewhere, the crew of the Deucalion prepares for battle at Trident Base. Learning of the existence of Slaine’s swift Tharsis, they are wary of its capabilities.
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.
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.
Inko and the others undergo piloting training in a Kataphraktos combat simulator. Inside, Rayet reflects on her hatred, anger, and fear towards the Mars Knights, as well as her own circumstances. Yagarai and Marito also use the simulator to recreate a past battle. And the truth of what happened on Tanegashima is revealed.
There were no traces of the battle that once occurred on Tanegashima, which was heavily damaged in Heaven’s Fall. When they arrive, Marito is flooded with memories of the fierce fighting there. But then, the Kataphraktos of a female Mars Knight comes at them relentlessly. Meanwhile, Slain, who has been acting without the knowledge of his superiors, acts recklessly.
To complete his plan, the Mars Knight relentlessly pursues Inaho and the others. Inaho is suspicious about the manner in which that knight fights. With backing from Marito’s group, Inaho begins a counteroffensive. Meanwhile, Slaine, unaware of the truth, has been ordered to provide support for the Mars Knight and is out in the field with him.
2014, fifteen years after a war between Earth and Mars. Desiring peace, Princess Asseylum of Mars holds a goodwill parade on Earth. Slaine a boy originally from Earth prays for her safety Meanwhile, on Earth, high school student Inaho and his friends receive pilot training in combat robots called Kataphraktos.