Sigh...your bf is not exceptional as I believe 99% men who work in Shanghai would have gf. I have 5 male friends, they all have gf in HK, but also have gf in SHG. 3 of them now married SHG ladies, and the 2 were being kicked back by their parents to work in HK because the parents don't like SHG women as they are more cunning and greedy in $.
It is very tempting to have a SHG gf. Most of them (esp. those who work for nightclubs) have fair skin, tall, good figure, young, good looking.
If he loves you, he should come back to HK. If he chose to stay, it means that not only he loves the job in SHG, but also the life and woman there.