The story revolves around Kio Kakazu. During a memorial service for one of his family ancestors he is introduced to a girl with cat ears. The girl calls herself Eris and claims she is an alien. Before long, fanatical alien worshipers and a mysterious government agency are in hot pursuit of Eris, but Kio's childhood friend Manami—who wants to follow in her father's footsteps in the CIA—captures Eris. Kio finds himself having to protect Eris from everyone.