Parallel Universe

Parallel universe/world or alternative reality is a self-contained separate reality coexisting with our own. Because "alternative reality" sometimes implies that the reality is a variant of our own, like for example a mirror world, we'll use the term "Parallel Universe" which is more general, without any connotations implying a relationship (or lack thereof) with our own universe (meaning a fantasy world can just as well have an alternative reality, doesn't need to be our reality). To put it more simply, this category is to show if more than 1 universe/reality/world is present in the anime.