In October 1941, society was threatened with destruction by the looming World War II. However, an even more unexpected obstacle arose: an invasion by extraterrestrial beings. Despite this unprecedented attack, the Axis and the Allies failed to join forces and remained locked in their destructive warfare. Thus, the fate of the planet rests on the shoulders of the Kishin Corps and their colossal Geo-Armor Robots, which were created by repurposing an alien robot soldier captured by humans. Taishi, an unwitting teenager, finds himself in the midst of this dangerous conflict over a mysterious black attaché case that was entrusted to him by his father, Professor Tokamura. The case holds a crucial control mechanism for one of the monstrous Geo-Armor Robots, which is coveted by the Japanese Kanto Army, the alien invaders, and the Kishin Corps. As spies, armies, and otherworldly invaders battle for control of the device and the fate of Earth, Taishi sets out on an epic adventure. However, in a world filled with giant robots, alien threats, and military might, will Taishi survive long enough to complete his mission?