Shiroi otoshimonotachi (2002)

Miho and Ei-chan, a young couple whose romance seems to be fading, have a fight on Christmas Eve. After they storm out of a restaurant together, they suddenly find themseves sitting outside a small train station in a remote mountain pass. The only people there are the elderly keeper of the lost-and-found desk who only explains that they have lost something they were searching for, and a young boy who won't say anything. They are soon joined by a number of others, including a schoolteacher, a worker from China, and a middle-aged mother, all of whom seem to be equally confused over why they are there.