The Dog Star, the place where beloved companion dogs go when they pass away before their human families. It is said that a year here is like a single day. And so, nine-year-old Tori arrives at this Dog Star. In this unfamiliar place, without her family, Tori is welcomed by a teacher and friends. The teacher says that if he sleeps for just a hundred nights, he'll be able to meet his family again. Having missed his family as soon as he arrived, will Tori be able to make it through those hundred nights?