The Shadow Line are steampunk-themed dark denizens who wish to consume the world in darkness. To achieve that goal, they send a Shadow Ressha called the Kuliner from their fortress Castle Terminal to gather the darkness in peoples' hearts by subjecting them to nightmarish scenarios to fortify the Shadow Line's railway to the point that there is a Dark Station in every city on Earth. The more inner darkness they gain, the closer to completion the railway will be until they are able to give their master Zett entry into the world. The plan is for Emperor to destroy all those among his followers that he deems useless.