A.D. 2001. The economy suffers from a lingering recession, crime is on the rise, the environment is under threat, morality has collapsed, the international situation is unstable…all in all, the future looks pretty bleak. Oh, and humans are also about to be conquered by alien invaders. With confusion reigning supreme, enter the invader hunters, members of the underground AEGIS Network resistance organization, who manipulate their pseudo-gate ability to hunt down the invaders. Gate Keeper Ayane Isuzu happens to observe Miu Manazuru, who has unusual telepathic powers. She reports to the AEGIS Network that she has uncovered a real gate telepathist, then one day Ayane asks Miu, “Do you really want to know about your power?” Miu then decides to follow Ayane. Suddenly invaders begin to appear in human guise!
Descriptions taken from AniDB.net