Fifteen-year-old Aiko has never seen anyone like her before - until Fletcher arrives at her orphanage to free her, and tells her that they're the last two Humans in the galaxy. Aiko can't accept that. How does he know they're the last two? What happened to the rest of the Humans? Finding the answers will require Aiko to follow a trail Fletcher abandoned many years ago, when he was just her age. But asking about Humans, it turns out, is the most dangerous thing she can do with her newfound freedom. It will take her to places she never dreamed of, and bring her face to face with a terrible truth...