Emilico is just one of many "Living Dolls" serving in the Shadows House, residents of which are pitch black from head to toe and constantly leak soot that stains the house black. Each "Shadow" is partnered with a Doll, which strangely resembles the other. As a Living Doll, Emilico must keep the house sparkling clean as well as act as the face for her master, Kate. In turn, Kate supports Emilico and treats her as her confidant.

As far as either of them can remember, this has always been the way their world works. However, the bond between a Shadow and a Doll isn't quite clear. Administrators watch over the young pairs from the higher levels of the mansion and judge them—but for what purpose?