Like the title asks. How many sapients are in Gensokyo, and what's the breakdown by location and race? This question's especially tricky since we have practically no data to go with. So, what would seem plausible?
My rough guess is ~1-2K per settlement, with another ~2K or more scattered through Gensokyo, not counting fairies. Iced Fairy guessed ~4-7K in the Human Village, and ~1-2K in the settlements. What's your guess?