>>35I've just looked through JRR Tolkien's book and inferred, that his Middle-earth world includes:
1. bacteria, because food rots;
2. gravity, because characters manage to walk and there is an atmosphere;
3. sun, because characters refer to it;
4. gravity implies that Tolkien's world is round.
5. chemistry, due to breathing, eating and sleeping of characters (including fantasy ones), meaning there are underlying chemical processes.
I'm pretty sure, we can find a lot of that crud in your Gensokyo too, because there are numerous pictures of Reimu defecating and eating crap.