In a strange world filled with sentient creatures of different species, an agreement called "The Promise" was made to end a long war between humans and the so-called demons. "The Promise" was an agreement where each would live in their own separate "worlds": the human world, free from the threat of demons; and the demon world, where human breeding farms were set up to provide food for the demons. By eating humans, demons take on their attributes which prevent them from degenerating into mindless monsters. In the demon world, a special breeding program was set up under the guise of orphanages; there, a human "Mother" would oversee the children to make sure they grew up as intelligent as possible. These children had identifying numbers tattooed on them and had no knowledge of the outside world. They believed that they were orphans and once they reached a certain age or intelligence, they would be taken out for adoption, but were fed to high-ranking demons instead.

In the year 2045, 1,000 years after the formation of "The Promise", you’re an 11-year-old orphan living in Grace Field House, a self-contained orphanage housing you and 37 other orphans. They lead an idyllic life, with plentiful food, plush beds, clean clothes, games and the "love" of their "Mom", Isabella. Their education is seen as an important part of their development, and you, with your two best friends Norman and Ray, always excel in the regular exams. The orphans are allowed complete freedom, except to venture beyond the perimeter wall or gate which separate the house from the outside world. One night, a girl named Conny is sent away to be "adopted", but you and Norman follow with her favorite stuffed animal toy. At the gate, they find Conny dead and discover the truth about their existence in this idyllic orphanage, to be raised as meat for demons. You and Norman plan with Ray to escape from Grace Field House with the children, but Norman is taken off to be "adopted". You and Ray then decide to escape.