The status of foreign labour in Japan after the quake has been a regular topic in the media and the Mainichi has an article (Japanese) on the subject . In short, it says that Westerners have mostly returned but Chinese are slower coming back. Yokohama's Chinatown employs around 2,500 Chinese nationals and some 300 students working part-time left. This has put pressure on local businesses and around 10 are still closed temporarily until they can be sure of staffing. Lawson had to ship in staff from head office to cope with the shortage. They also mention that one of the Chinese graduate trainees they accepted has since declined the offer.
Elsewhere, the textile industry in Japan employs some 40,000 Chinese nationwide, some as part-timers and some as trainees. A spokesman estimates up to 30,000 left and have not all returned. Many of those who did leave have said their families back home were concerned. Trainees and overseas students tend to be mostly young so are more likely to have faced that pressure. The article also mentions that young people likely have less money for airfares so are perhaps reluctant to lay out return tickets. Meanwhile, Berlitz apparently lost around 30-40% of its English teachers but 90% of those who left are said to have returned.