In 1969, Tokyo is a technological, scientific and industrial center. However, behind the scenes, a malevolent force known as the "Invaders" is secretly infiltrating the population. The true identity of the Invaders remains unknown to everyone except for the covert agency called AEGIS. AEGIS combats the Invaders, but it is only the Gate Keepers who possess the power to open portals to other worlds who can truly defeat the Invaders. The Gate Keepers are an elite team of extraordinary individuals with special Gate-related abilities who are humanity's only hope against the Invaders. Shun Ukiya is an ordinary high school student residing with his mother and younger sister after his father's death. One day, he discovers a group of Invaders on their way to attack his family. In a desperate attempt to save them, Shun discovers his ability to open Gates and harness incredible power. His newfound talent catches the notice of AEGIS, particularly his childhood friend and Gate Keeper Ruriko Ikusawa.