If the world where we live is an inside in the cave planet????The boy getting on a mysterious railway and starts on a journey to save father who knows the secret in the planet. Fantasy of new type that dragon and magic do not appear. This is the world that no one has seen. It is serialized in the Japanese magazine "Comic gumbo" and "Comic Zero-1", and this Sci-Fi fantasy comic revives by full color. "Salvo-1" is free. 2,3,and 4 is published one after another. Please retrieve it by the name of the author, the work name, and the name of the developer.