There is a strong predilection amongst Asian girls to go for white guys. Despite what someone posted previously, the outmarriage rates of Asian Females is distinctly skewed to outmarrying specifically to marrying White Males, you can see this in the Census Bureau's statistics.
It's on the order of something like 25% while other outmarriage rates of other races are in the single digits here in the USA. Which still leaves 75% of AFs marrying within race.
There are multiple reasons, but those are neither here nor now, and nor will knowing or discussing the reasons help in PUA. It simply is, accept it and adapt it into your PUA framework whether your white or Asian.