There's plenty of reasons for this...
White dudes go for Asians because they assume they're submissive, sexually inexperienced, and much better looking than themselves. Honestly, some white dudes wouldn't even pull a below average white chick but maybe an above average Asian chick that's trying to get out of her country... Some dudes in military also wife up known Asian slores because of looks and how they treat them
Some Asian chicks view it as a sign of status. The whole "white is right" thing so some see them as priviledged people because of their skin tone. I mean think about it... This entire planet has gassed up the white race basically. But their are others that just want to get out of their country to become American citizens. And some Asian men are really hard/disrespectful to their women
So i dont know.... Their are other reasons too. I've actually seen more Asian/black marriages than anything... But I've mainly hung out with black ppl. I've dated Asians too, they're cool. It's hit or miss... I've never been to Japan but I've experienced the way some of the women treat you and it's