Yeah, what the anon above me said. It's like in Tsubasa Reservoir Chronicle. Kurogane comes from a Japan, but it's not the same Japan as the world of xxxHolic where we're introduced to him (fuck yeah dimension travel!), for example. Likewise, the first four Pokemon regions are part of a () (fantasy) Japan, but definitely not the Japan we know exists in our world.

/is clearly having too much fun with this multiple worlds shit