If it is due to long-lasted hatred, then it could have been ingrained into them from a young age.
Anyway, the thing is that maybe the Japanese boys are happy with their Japanese girls, and the Chinese boys happy with their Chinese girls. An vice versa for girls to boys.
The thing is, that different nationals (people for different countries) are completely different people. I'm sure Japanese do go with Chinese, but it doesn't happen as much as people to their own countries.
It's unfair, like yukio_michael said, to 'pimp' chinese girls to the Japanese.
You aren't helping anything or anybody.
If a nihon-jin and a chuugoku-jin decide to go together, they will, and they don't need threads like this to help them along.
Lol, I'll shut up now.