How about a youkai who can understand all languages? Like a universal translator.
This is the best suggestion yet. If we have a translator youkai, that means ZUN would need to create at least one foreign cast member to join Gensokyo. There could be some sort of incident - any one will do - and of course everyone blames the immigrant, right? Only when they round on the immigrant youkai, she tries to explain that it's all a misunderstanding but no one can understand what she's saying. And being an immigrant youkai, she of course has a huge family
1 who will back her up in a fight. Who, oh who, will step in and clear up this misunderstanding once and for all, and save Gensokyo from the ruin of total war? Why, universal translator youkai, that's who.
1 Not meant to be taken seriously; I'm an immigrant myself. We foreigners enjoy playing with the stereotypes.EDIT: OK, the more I think about this idea, the more I feel like scripting it. Here's a very, very rough sketch:
Stage 1: PC is all "I can't believe [incident] happened! I'm so angry, and I bet that foreigner who just moved in, the one I've been hearing everyone talking about, is behind it all! Just wait till I get my hands on her!" PC fights fairies. Stage 1 boss appears, who's all "Oh I know where the foreigner lives, but I'm not telling you ... unless you fight me!" Fight ensues, PC wins, Stage 1 boss is all "ugh ... just head towards that mountain pass near the border".
Stage 2: PC travels through mountain pass near the border, fights fairies. Stage 2 boss appears and is all, "hey this is private property" but PC says "I'm after the foreigner who caused [incident]!". Fight ensues, PC wins, travels onwards.
Stage 3: PC is further up the mountains now, fights fairies. Stage 3 boss appears, who says, "but the foreigner is innocent! I know her personally. I can't understand a word she's saying but I know she has a good heart!" PC doesn't care, fight ensues, PC wins. Stage 3 boss is all, "ugh, I can see you won't give up. She lives in that cave on top of that mountain, right at the border."
Stage 4: PC travels up to the cave, fights fairies. Stage 4 boss appears, and her dialogue is indecipherable gibberish, but she appears clearly agitated and frightened, then angry. Fight ensues, PC wins, she decides to see if this youkai has a family.
Stage 5: PC heads further up the mountain, fights fairies. Suddenly, three youkai appear, who resemble the Stage 4 boss and speak the same gibberish. They look pissed. PC is all "uh oh, this must be the family." Fight ensues, a brutal attack from three directions. PC wins, decides to head back down the mountain to gather forces to come back up the mountain and exterminate all the foreigners.
Stage 6: PC heads back down the mountain, fights fairies. Before she even reaches the cave again, Universal Translator Youkai appears. She has with her Stage 4 boss, and the three Stage 5 bosses. Universal Translator Youkai says it's all a misunderstanding. The four foreign youkai speak, and she translates for each of them, as they give a fuzzy description of the person they saw who really is behind [incident]. At this point, PC is given a choice in dialogue responses:
1. "Boy, I feel foolish. I'm sorry for jumping to conclusions!"
2. "Yeah, right. That's exactly what a guilty person would say!"
If the PC chooses 1, Universal Translator Youkai will be all, "well, you still have to be punished anyway." Fight ensues, and it's PC vs. Universal Translator Youkai and Stage 4 boss at the same time. At the fight's conclusion, the real person behind [incident] is revealed in Extra.
If the PC chooses 2, Universal Translator Youkai will be all, "you need a lesson in multiculturalism!" Fight ensues, and it's PC vs. Universal Translator Youkai, the Stage 4 boss, and all three Stage 5 bosses at the same time. At the fight's conclusion, the real person behind [incident] is revealed in Extra.
In both Extras, the real cause of [incident] is Yukari, who wanted to teach PC to appreciate beings from other parts of the world. And because she was bored.