Scientist Mamoru Kazuki uncovers an impending alien invasion of Earth by the Izaru, a race present since the dinosaur era driven to conquer by their own dying planet. To counter this threat, he conceives and builds the giant robot Gakeen, harnessing advanced magnetism and sphere joint theory. This defense requires two pilots operating specialized Magnetman Plus and Magnetman Minus units that physically merge to form Gakeen. One pilot is his daughter, Mai Kazuki, who endures a dangerous augmentation to interface with Magnetman Minus. The other is new world karate champion Takeru Hojo, recruited to pilot Magnetman Plus. Mamoru Kazuki both creates this defense system and strategically leads Earth's counteroffensive against the Izaru. His scientific work directly powers Earth's defense.