I think some of the most beautiful couples are black x Asian, from what I know, Asians are very particular in keeping things within their race, and aren't too accepting of others(again this is looking outside in). Considering you are just as genetically different to another Japanese person as to a black person, it shouldn't matter. But Cultural wise, I understand trying to keep traditions and what not alive. I am assuming you wouldn't simply approach a latina or a black person in hopes of romance, so you are probably more aware of who you select