Riro
The alien behind the attacks on Earth. She is physically the youngest of all the aliens. Over a hundred thousand years ago, Riro came to Earth and gave her glasses to a young primitive girl. These glasses were the catalyst that lead to the formation of human civilization. Riro's glasses eventually ended up in the possession of Yuuki. Without her glasses, Riro's heart became cold and she lost all emotions save for the desire to destroy. She is redeemed once Yuuki returns her glasses. Riro and Yuuki form a close bond by the end of the series.