People always say, "The blue sky falls from the blue and the underworld falls to the underworld." But I don't know if there is really a "underworld" in this world. However, I have seen a lot of creatures that are called "ghosts" by the world. They can be said to be of various kinds. They wander in this world with their own obsessions. They are so lonely in the long years, and slowly forget themselves, leaving only the deepest memories in their hearts waiting for the destined person to listen...