An asian woman living in Japan who speaks Japanese? The only aspect that feels Korean is the way she spelled Kwannon. Korea has "kw" in words, Japan doesn't. Japanese just renders it as k. While we have little other info to work on.... It's interesting food for thought.
It IS true that there is a small subset of Japanese society that are people descended from Koreans. Most of them are relatively poor too. So, it does make sense for an organization like the Hand to use them as agents. We don't have a lot to go on though. Yes, she was romantically involved with one or more Japanese men, but... that's not really saying much. there's quite a few mixed heritage people in Japan. Some of them might not even know since mixed korean/Japanese... isn't very interesting looking. Sure there's differences, but very subtle ones.