UFO, flying saucers, I wonder if they do exist? What about Nessie? The Abominable Snowman? Ghosts…? They may exist or they may not. Our world still has mysteries that cannot be explained by modern science, and people can often attribute supernatural nature for things that they can’t understand. But what if there’s a parallel world where all that can be real? There are those who believe in the existence of multiple worlds, at least in theory. It’s not possible to tell for sure, but in the world of this manga, they do exist.