I've met a few people in Japan of Korean ancestry and they have all mentioned they have a very hard time fitting in and meet a lot of discrimination still everyday. I was always reluctant to dig deeper because you can definitely feel that it's a still a very open wound and something they're still actively dealing with every day.

Some similar anecdotes, while working in a Japanese office there is one co-worker whose great-grandfather was Italian. I haven't seen any actual discrimination against him, but some people are definitely happy to let you know that he is not full Japanese, so I'm certain he's ran across some for his ancestry.