"Gundam Reconguista in G" is set in the Regild Century (R.C.), a distant future where humanity has rebuilt civilization after the devastation of the Universal Century. The story centers on Bellri Zenam, a young cadet of the Capital Guard, a military force tasked with protecting the orbital elevator known as the Capital Tower. The world is divided into factions, including the Capital Army, the Amerian Army, and the pirate-like Megafauna, all vying for control of resources and technology.

The narrative begins when Bellri encounters Aida Surugan, a member of the Megafauna, who is attempting to steal a powerful mobile suit, the G-Self. Bellri inadvertently pilots the G-Self, forming a connection with the machine and becoming a key figure in the unfolding conflict. The G-Self is revealed to be a highly advanced mobile suit with unique capabilities, drawing the attention of multiple factions. As Bellri and Aida are drawn into the escalating tensions, they uncover secrets about the world’s history, including the existence of the "Reconguista," a plan to restore humanity’s connection to space and reclaim lost knowledge.

Throughout the series, Bellri and Aida navigate shifting alliances and moral dilemmas, encountering characters such as Klim Nick, a rival pilot from the Capital Army; Noredo Nug, a fellow cadet with her own ambitions; and Raraiya Monday, a mysterious girl with ties to the G-Self. The story explores themes of war, ideology, and the cyclical nature of history, as the characters grapple with their roles in shaping the future. The conflict intensifies as the factions clash over control of the orbital elevator and the G-Self, leading to large-scale battles and personal confrontations.

The series concludes with a resolution that emphasizes the importance of understanding and cooperation, as Bellri and his allies strive to break the cycle of conflict and forge a new path for humanity. "Gundam Reconguista in G" combines political intrigue, mecha action, and philosophical undertones, offering a complex narrative that reflects the broader themes of the Gundam franchise while introducing new elements to its lore.