Okay, that may sound a little confusing, and no, not looking for the name of a zoo or theme park here XD
Essentially, simply put, I'm writing a novel, and for that, building a world around it. Yes, there is no need for the Kanji - I am well aware of that, and yet, I feel like using kanji for specific phrases.
My story has several locations. Much like a heaven - earth - hell, except they are based on a reincarnation and enlightenment system instead of an afterlife based on a moral judgement sort of thing. Those souls that achieve enlightenment and 'ascend' beyond their eternal cycle of death and rebirth in Jinkai by discarding their current worldly attachments, go to Tenkai, where celestials and other deities live. And "hell" is fully inhabited by demons, not inherently evil, merely fundamentally different to those that live on "earth". Yes, sinners and saints don't matter in this universe. Morality is a human construct (at least in this story if you would disagree on that, as I really don't want to be dragged into a meaningless debate).
Anyways, the three worlds are as such:
Tenkai - Celestial World (天界)
Ningenkai/Jinkai - Human World (人界/人間界)
Makai - Demon World (魔界)
Particularly, using Yōkai instead of another phrase for Demon, such as Akuma, as that would be more 'Devil' I believe, and would have more 'Evil' connotations. I thought of using Mazoku, except that implies 'Demon Race', as in a singular species. I want 'Demons' in Makai to be the equivalent of all 'Organisms' on "Earth", as opposed to merely being the opposite of Humans. (But, I would very much appreciate if someone could provide a general term as such to use the would imply Demons - or even something like "Others" as in fundamentally different from Earth's inhabitants, as Yōkai's meaning is closer to ghosts and strange apparitions.)
As such, here I come to the crux of the matter. Particularly, the naming of the Human World. I believe that sounds rather pretentious, as Humans alone are not the inhabitants of Earth. Yes, they are the apex predators and all that, but to keep Makai and Jinkai parallel while giving the impression that Makai is not of only one species, but composed of several diverse set of beings that are merely fundamentally different to all creatures on earth. As 魔 (Demon) is up to interpretation, it does not have the same problem. For example, there would be demonic equivalents of dogs and bacteria as well, on Makai.
So, is there another prefix I could use, instead of Jin or Ningen, that would imply all the known organisms on earth (animals inclusive of humans at least, preferably others outside the animalia kingdom as well, such as microorganisms)? I would also like it if it is simpler in terms of the number of syllables, even if the term itself is particularly obscure.
I understand this is a very tall order, on top of a very lengthy request. I think the above would be important context as to understand the exact implications of my query. If not, I apologize for the long read, so thanks for at least putting up with me XD Thanks in advance for the assistance as well, if I may be so forward as to presume as such? :D