The story takes place in a parallel world that resembles modern Japan, but where alien lifeforms known as "Kikō" (Trick) fell from the sky ten years prior and started attacking humanity. The main characters are a pilot, Mizuru Mido, and her assistant, Fuu Sagami, who use a mecha made out of an enemy's remains. However, battle causes memory loss for the pilot, and they must unravel the mystery as to why.

[Source: Anime News Network]