Aoba Watase, a high school student, finds his life upended when he is suddenly thrust into a futuristic war involving giant mechs known as Luxon. During a routine day, Aoba is attacked by a mysterious mech piloted by a girl named Hina Yumihara, who claims to know him from the future. Before he can fully comprehend the situation, Aoba is rescued by Dio Weinberg, a pilot from the Free Pact Alliance, and transported to their military base. There, Aoba learns that he has been brought 70 years into the future, where humanity is divided into two factions: the Free Pact Alliance and the Great Zogilia Republic.

Aoba’s arrival coincides with the development of the Coupling System, a revolutionary technology that allows two pilots to synchronize their minds and enhance their mechs’ combat capabilities. Aoba demonstrates a natural aptitude for this system, forming a strong Coupling bond with Dio. As Aoba adjusts to his new reality, he becomes a key figure in the Free Pact Alliance’s efforts to combat Zogilia’s aggressive expansion. The conflict escalates as Aoba encounters Hina again, discovering that she is a soldier from Zogilia with a mysterious connection to him. Their interactions hint at a deeper, unresolved relationship tied to the future.

The narrative explores the complexities of war, loyalty, and the consequences of time travel. Aoba’s journey is marked by his struggle to reconcile his past life with his new role as a mech pilot, while also uncovering the truth behind Hina’s knowledge of him. The series delves into the motivations of both factions, revealing political intrigue and personal vendettas that drive the conflict. Key characters, such as the stoic Dio, the enigmatic Hina, and the determined Aoba, are developed through their interactions and growth in the face of escalating battles.

As the war intensifies, Aoba and his allies face numerous challenges, including betrayals, shifting alliances, and the moral dilemmas of warfare. The story builds toward a climactic confrontation that tests the limits of the Coupling System and the bonds between the characters. The series concludes with a resolution that ties together the threads of time travel, personal relationships, and the broader conflict, leaving a lasting impact on the world and its inhabitants.