Miyashita Megumi, also known as "Gumi", was one of the only survivors in a plane crash thirteen years ago. Since then, she has been able to see two copies of every person and one of them always has a "C" on them. Thirteen years later, she now wears glasses, yet her left eye remains a puzzle. And then, her friend goes "missing".

Based on the Vocaloid song of the same name: http://www.nicovideo.jp/watch/sm15230821