Gate Keepers

It is Tokyo, 1969. Earth is under the attack of the "Invaders." Fortunately, though, the public is unaware of this. But to the secret orginazation, A.E.G.I.S., the threat is very real, and it is up them to stop this invasion. One day on his route to high school, Ukiya Shun observes a battle between a young girl and a group of Invaders. (myanimelist.net)