Can anyone tell me the relationship between Eirin and Sakuya?
Last I checked, there is no answer to this whatsoever. So feel free to make up whatever you want.
Anyway, I've been intentionally avoiding this thread for a while now, but I just noticed that there seems to be some discussion over the fact that the Lunarians say they don't like killing. Some people take it at face value, and others reject it because it seems like they're just trying to look nice despite their cruel actions.
Of course, both of those answers miss the
real point, which has everything to do with the Shinto concept of "kegare" which has been translated as "impurity". Basically everything anyone on the moon does ever has everything to do with impurity, and the avoidance of it. Impurity is associated with death, and is a bad thing. Shinto doesn't like impurity. You have to clean yourself before visiting shrines, and you're expected to avoid shrines if there's been a death in your family recently. There's even a subtle caste system in Japan revolving around families whose jobs deal with corpses, who are traditionally shunned and even now can have problems getting jobs. Point is, cleanliness is divine, and death is unclean. In the Touhou-verse, this is taken very far to the point where impurity is the only reason things die in the first place. So the Lunarians moved to the moon to get away from impurity, and drive off outsiders to keep impurity away. When Reimu threatens to shoot impurity, this is the only moment when Yorihime gets serious. This is just something they care about.
Which is all to say that they don't like killing on the moon because it gets the floor all dirty. It has nothing to do with morality or mercy or posturing or anything. It's just very messy and distasteful (in an almost sacrilegious way). This is also why they have no problem whatsoever slaughtering people who aren't on the moon. By the way, please try to stop tracking blood on all our carpets, filthy Earthlings.