Shun Ukiya is an unprepossessing hero, a goofy kid who's read too many comic books. In 1969, as Japan enters its postwar economic boom, sinister alien invaders are attempting to take over the Earth. The lock-stepping aliens can only be defeated by the Gate Keepers, young men and women with the psychic power to channel energy from other dimensions. These teenagers are sought out and trained by the Earth Defense Force, A.E.G.I.S.. Shun is recruited and at the special high school, he meets other agents he'll be working with including mechanical whiz Megane, infantile musician Reiko, and Ruriko, whom he knew as a child.