"Kishin Taisen Gigantic Formula" is set in a world where humanity faces an existential threat from an alien race known as the ES-WORM. To combat this menace, nations across the globe develop massive humanoid weapons called Gigantic Formula Units, each piloted by a young child due to their unique ability to synchronize with the machines. The story centers on 13-year-old Reiji Takuma, a boy who becomes the pilot of the Japanese Gigantic Formula Unit, X-ARG. Reiji is initially reluctant to take on this responsibility, but as the ES-WORM attacks intensify, he grows into his role as a defender of humanity.

The narrative unfolds as Reiji and other child pilots from various countries are brought together to form a united front against the alien threat. Each pilot carries their own personal struggles and motivations, reflecting the broader geopolitical tensions and alliances among nations. The series explores themes of sacrifice, camaraderie, and the burden of responsibility placed on young shoulders. As the battles escalate, the pilots must confront not only the ES-WORM but also the moral and ethical dilemmas of wielding such destructive power.

Key characters include Reiji’s childhood friend, Akira Kageyama, who provides emotional support and a grounding presence, and the enigmatic scientist Dr. Tatsuma Ichinose, who oversees the development of the Gigantic Formula Units. The series also delves into the dynamics between the international pilots, highlighting their cultural differences and shared humanity in the face of a common enemy. The plot builds toward a climactic confrontation with the ES-WORM, testing the limits of the pilots and their machines while raising questions about the cost of survival in a war-torn world.