Kuji-kiri said: Nope, just happens in the Battle Royal doujin. ;)
And in the manga Kurohime... and in various other fairy tales and assorted works of Japanese fiction, hence the question. It would be better to ask, do "Touhou" oni lose their powers when their horns are broken. Given the artist just had Reimu do it to Suika as a gag, I'd say no, but that tells us nothing of canon. Only ZUN knows for certain and I doubt he's even given the matter any thought.
I wanna see Remi's crying face so do it Remi! do it for ME...um i mean for Reimu
Huh?WWWAAAAAAAAAHHSo in the end, all she accomplished was getting one of her horns broken off...Well then, Milady...NOWAYNOWAYNOWAY! You saw what just happened, didn't you? Why do I have to go try something that ended so horribly?!...if you please. ☆Yes.Really? I have to?Please don't worry about it; I'm sure they will regenerate in two to three days' time.Don't worry. If it's you trying, Milady, I'm sure you'll succeed.By "if you please", do you mean I have to do it?Yes.She just ripped off an oni's horn, you know!? I could get my wings torn off or something!*forcefully pushing*