There is a man who is a pretty high up partner at my company--he is Korean. He met a new hire (this was at the airport, we had to travel to be on site for something vs doing zoom) and we were there for a long time due to weather delays. I can't remember the exact words he used but he ended up somehow asking for trying to guess what ethnicity the new hire was (he was also Asian) and it came out that he was Chinese. The partner said "Oh good. Glad you aren't Japanese!"I thought it was so so weird at the time but I didn't get it. Then I thought it might be just something I don't get because I am not Asian (I am middle eastern and there are all sorts of weird things we might say that other people would bristle at). I asked my Chinese friend about it and she told me that Koreans hate Japanese people. I researched that a bit and there are definitely anti-Japense sentiments amongst a large portion of Korean people. This partner has a tendency to say offensive things about people (not necessarily with a racial/ethnic lense though). Would you say anything to anyone? I ended up talking to a peer about it and she told me she once saw him ask a Chinese person his last name and then reply "good" when it was a Chinese one, so this is a pattern.