Ah, my apologies. Most people can't pass between them, but there are a number of different universes out there. They can be as similar as just a slight change in events, or so different that even the basic laws of nature and magic are inconsistent between them.

For example, as far as I know, the world I'm from has no true yokai, but does have at least one divine being that existed before I Ascended. On the other hand, someone I know from another world is a very powerful kitsune.