Imagine waking up to find yourself in one of those "the mice and other small animals have a secret civilization hidden from humans" settings. And you've been turned into a mouse and you're horrified to discover that you were already living in that sort of setting but there's some sort of weird perception filter that causes mice to appear as nonsapient animals acting on instinct instead of the sapient creatures they actually are. Like, human brains cannot comprehend the mouse society. It's like an entirely separate wavelength of the same reality. Language becomes squeaks, furniture becomes scraps and rubbish, furnished homes become a dusty hole. You had no idea it was there, because you couldn't have any idea.
And if that existential horror wasn't enough, it becomes clear that the perception filter works both ways, and humans no longer appear sapient to you. You can read the books in your local mouse library just fine, but the human road signs? Incomprehensible scribbles with no rhyme or reason. The humans are lumbering, unpredictable creatures which fashion large structures with bizarre, barely comprehensible purposes. They don't seem sapient, they seem monstrous. Just as wild as a mountain lion or an eagle, and just as threatening, yet their excess materials are strangely useful. It's terrifying. Every once in a while you manage to identify something with how it is in your human memories, you can extrapolate what the humans must be doing or saying because you remember what the human context is, but you cannot recognize human civilization anymore. Because you're a mouse now, living in a mouse's reality. And nobody else has been through this, so nobody else in this mouse world can understand what it is you're going through. And you're so small.
Anyway would that be messed up or what? Give me some mildly horrifying mouse world isekai.
