Force of habit [shrug!] if you really want the details, it's like this: Our world is separated into the realm where humans dwell, the realm where spirits dwell--some would call it "the afterlife"--and the realm where demons dwell. That doesn't mean that any of these factions stay in their own domain, no, demons slip through to interact with humans, humans end up in the demon realm accidentally or come to the spirit world when they die. Demons these days aren't causing very much trouble, but in case they do we have our Spirit Detective to deal with them. He takes on "cases" day to day to keep the balance between all three worlds.

[That sure was an exposition dump.]

Actually, two that are here now are demons, one is the Spirit Detective I mentioned.

[Something occurs to her! Is it the fact that she forgot to mention how she factors into all of this? Nope, of course not.]

Oh dear, that was inaccurate, we have myself and four others from my world as far as I know at the moment. This one's just a regular human, though she knows a little bit about the goings on I'm mentioning. [Depending on what time she's from anyway, her knowledge varies.]