The Landing Castles of the Mars Knights that have landed on Earth launched an attack using Kataphraktos with the aim of invading the planet. The United Forces of Earth launch a counteroffensive. As the fierce battle rages on, Inaho encounters a mysterious girl.

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.

Slain has misgivings about the war. However, he has no allies around him and no way of telling who the enemy is. Meanwhile, Inaho is entrusted with a secret request by Seylum as Rayet, who is hiding her own true identity, is on edge.

Rayregalia, ruler of Mars, orders that an investigation be conducted on Earth. Slaine takes advantage of this opportunity to speak with the Martian emperor in person. Elsewhere, the assault landing ship that Inaho and the others are aboard has been sailing on a course to reach United Earth HQ.

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.

Inaho and the others are hard pressed in their fight against the Martian Kataphraktos. But then a mysterious fighter craft appears and joins the battle. Elsewhere, Darzana and her crew hide the damaged assault ship in a dock, and there, they discover a combat mecha of unknown origin.

Slaine is interrogated under the assumption that he knows something. Slaine manages to keep silent and not reveal the truth, thinking back to the time he once spent with Princess Asseylum. Meanwhile, Count Saazbaum seems to have ulterior motives of some sort.

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.

Seylum thanks Inaho for everything and then leaves. Elsewhere, Slaine learns Count Saazbaum’s true motives. Yagarai gives Capt. Magbaredge Marito’s patient chart. Feelings begin to stir within each of them.