Gate Keepers

Gate Keepers (ゲートキーパーズ, Gēto Kīpāzu) is primarily a role-playing video game for the PlayStation. The game was then adapted into a manga series written by Hiroshi Yamaguchi (山口 宏, Yamaguchi Hiroshi) and drawn by Keiji Gotoh and an anime series produced by Gonzo, and first aired on April 3, 2000.

A six episode original video animation (OVA) sequel, Gate Keepers 21, was released in 2002. The main characters in the OVA sequel were the next generation of Gate Keepers.

All incarnations of the titled Gate Keepers series, follow the same basic premise and share most of their characters, with some major discrepancies (mainly involving the character Reiji Kageyama). A character from the game, Francine Allumage is completely absent from the anime. Another character from the game Misao Sakamori, was replaced in the anime with the new original character Megumi Kurogane (though Misao does make a guest appearance towards the end of the anime).

Plot

The story is set in 1969, a period of time in which Japan is experiencing intense economic and social development after the end of World War II in 1945. Unbeknownst to humans, alien/interdimensional beings have emerged with plans to take over the world by sending numerous agents to wreak havoc in cities, turning people into robotic minions. They are referred to as "Invaders" (インベーダー, Invēdā).