A deep realization that everyone is on a secret, and you've been let out.
You don't know what it is, if it's macabre or if not knowing could kill you, but you know something is wrong.
People in the village start to silence when you come around the place, and they avoid you like the plague.
One day, you confront a drunkard that is well enough out of it to answer to you. It turns out you are the only human around. They are anthropomorphic enough, yes, but they live with in a sort of hivemind, a collective conscience that only feels natural to them. In every sense, they are just like humans, except they can't understand conscience, or feeling. Instead, they just use a chinese room sort of empathy. They know how to react, they do so even better than regular people (they will throw themselves in front of cars to save a puppy) but it's not real.