Asaba Naoyuki is an ordinary high school student. As a member of his school's press club, he's just spent the summer camping outside the local military base, in hopes of seeing the UFOs that are secretly kept there, according to local legend. Returning to school, he meets a strange girl, Iriya Kana, and gradually comes to realize that she is more than merely strange - and that a dark secret lies beneath the world that he knows.

Asaba Naoyuki is an ordinary high school student. As a member of his school's press club, he's just spent the summer camping outside the local military base, in hopes of seeing the UFOs that are secretly kept there, according to local legend. Returning to school, he meets a strange girl, Iriya Kana, and gradually comes to realize that she is more than merely strange - and that a dark secret lies beneath the world that he knows.

"I've lost my memory, I'm estimated to be 13 years old, and I might be the last surviving member of the human race - but it's okay. I have everyone with me. I have Spike, Angela, Cleric, Reeves, and Trigger. So it's okay." One day, Haruka, a girl who lives in an abandoned building with robots that are like family to her, sees a girl who looks just like her. - Could it be that there is another human being alive besides her? After an extensive search, she finally meets the girl who introduces herself as Eva, but her true identity is... (Source: Kadokawa, translated)