So, I hope I can give enough details about this. I want to surprise my gf by finding this for her. She was young and in Hong Kong when she read these so probably 15 years ago or so (the comics themselves could be older) and I imagine it would have been in Cantonese (the comics could have just been translated from Japanese or Mandarin).
Basically a girl finds a fox or a boy who can turn into a fox, and there is also another boy who can turn into a (black) fox who is like a bad version or something? They may or may not have been ghosts.
That's really all the information I have. I don't want to straight up ask her the name of it (don't know if she even remembers the name) because she would know I'm looking for it.