On her way to make up with her childhood friend Arata Kishimo and tell him how she feels, high-schooler Mio Miyamasu is struck by a car. She wakes in the World Border, a way station where the recently departed name their dearest wish and step through a door to it, guided by a talking plush mascot named GiMON. A girl called Kiku stops Mio at the threshold: she isn't dead, only out of body. Mio sets out across the World Border to find her way home.