Gensokyo, the land where common sense doesn't exist.
It's always described as a usually peaceful place, where youkai and humans live, sometimes, an incident happens and everyone goes nuts over it. After over 20 incidents in the last years, the peace was broken completely.
Youkai constantly eating or hurting humans who exited the village, religion wars, lack of respect for even their same species. It's a complete chaos and restoring the tranquility is going to be very hard...

Hakurei Reimu, Shrine Maiden of the Paradise, wonders if all this chaos is due to another incident, but it's so baseless that she can't just go waste time on something that may or not have a culprit.

Reimu "I hope this ends soon, or they will destroy my shrine."

Yukari: "You are worrying too much, the nature of youkai is like that, you can't force a human-eating one to not do it."

Reimu: "But this is not about the youkai we are talking about. The human village is too unpeaceful these days, and there might be a youkai causing this."

Yukari: "What if, they want peace between both races?"

Reimu: "What are you implying? That will never happen, you know that if something like that happens, youkai will dissapear, that buddist monk tried it and didn't work as expected."

Yukari: "I know what would happen, since youkai are nothing but creation of the human's fears. But don't you think this is really weird?"

When Yukari finished that line, a trumpet melody was playing from far away, taking the attention of the shrine maiden.

Reimu: "What's that melody? From where does it come?"

Yukari: "What melody?"

Reimu: "Can't you listen? It's a trumpet sound, the melody is really nice."

Apparently, Yukari couldn't listen the melody at all, but realized there was something wrong with that.

Yukari: "I can't listen to it at all, but it seems you will have to go to the human village to discover who's playing that... I'm sorry, somehow i feel strange" 

She fell asleep. Reimu, curious about the stange melody goes in search of the one playing it, will that have any relation to the human village's chaos? Is it some youkai conspiracy?