"Aldnoah.Zero [Re+]" is a recompilation of the original "Aldnoah.Zero" series, condensing the two-season narrative into a more streamlined format. The story is set in an alternate timeline where humanity has colonized Mars after discovering advanced alien technology known as Aldnoah. This discovery leads to the establishment of the Vers Empire on Mars, which declares independence from Earth. Tensions escalate into a full-scale war after the assassination of the Martian princess Asseylum Vers Allusia during a peace visit to Earth, an event orchestrated by Martian hardliners to justify an invasion.

The conflict centers on the disparity between Earth's underdeveloped technology and the overpowered Martian Kataphracts, mechs powered by Aldnoah. Earth's forces rely on ingenuity and adaptability to counter the overwhelming Martian advantage. The protagonist, Inaho Kaizuka, a calm and analytical high school student, becomes a key figure in Earth's resistance. His tactical brilliance and ability to exploit the weaknesses of Martian technology make him a formidable opponent. Alongside him is Slaine Troyard, a Terran-born Martian who is deeply loyal to Princess Asseylum and struggles with his divided loyalties as the war progresses.

Asseylum, believed dead, survives and goes into hiding, witnessing the devastation of the war firsthand. Her ideals of peace and reconciliation clash with the harsh realities of the conflict. The narrative explores themes of betrayal, loyalty, and the moral complexities of war, as both sides grapple with the consequences of their actions. The story is marked by shifting alliances, political intrigue, and the personal struggles of its characters, particularly Slaine, whose actions become increasingly driven by his desire to protect Asseylum and his growing disillusionment with both Earth and Mars.

The recompilation retains the core elements of the original series, including its intense mecha battles, strategic warfare, and character-driven drama. It emphasizes the central conflict between Earth and Mars while delving into the motivations and moral dilemmas of its key players. The streamlined format provides a cohesive viewing experience, focusing on the pivotal moments that drive the narrative forward.