Yuru is a young hunter in a mountain village sealed off from the outside world, where a few people command paired spirit creatures called Daemons. Nobody will tell him why his twin sister Asa is kept caged inside the village, carrying out a duty she is not allowed to explain. When the Kagemori storm the village with modern weapons and Daemons of their own, one of the attackers is a woman identical to Asa who claims to be the real one. Two Daemons wake at Yuru's side, and he leaves for the world outside to find out which sister is his.