This is new to me. I’d suspect that people who grew up in a country where everyone pretty much looks the same, they would feel attracted to their own race. Sure, some people have a preference I guess? I think that everyone worldwide is struggling finding a good life partner, especially in economically successful countries because there’s no need to couple up to survive. As for Japan, there’s an issue about women becoming very left-leaning while men becoming more right-leaning. There’s a large gap that’s becoming bigger every year. So, the government realized that if they don’t do something, the birth rates will get even worse. Not sure if white supremacy has much to do with it. If that was the case, the solution would have been to attract white immigrants to Japan so that locals could couple up with them and create mixed families.