Asian Angels (Celestial Maidens)

I'm looking for information on Asian angel myths, specifically the one that is alluded to in the manga "ayashi no ceres". (it's similar to the selkie myth too.)

I'm not looking for information about the Manga, I'm looking for information about the original myth, which I know exists and I've read somewhere, but for the life of me, today I can't find any good "hits" for it! I tried the library and the bookstore to no avail, and the internet often gives so many false positives.

I want a really good source for this folklore please! If at all possible, I'd like to know if there is a specific Korean version of this tale with angels called "Shyun-nyur".

Thanks so much!