That could be due to being away from friends and family and a failure to build new connections within their new nation

From what little I understand for Confucius Nations they don't really have away for people to integrate and be classed as

Korean, Chinese Japanese or other it a person from the west or Africa moved to Far East they will never be seen as one of them

Also their are the cultural and social expectations that can be very different modern life can also be to blame as well

Human beings were not designed to be happy they were designed for survival due to evolutionary pressures

You can live somebody, do things farther be very cooperative as well as anything else to try to make people happy

But they would still be unhappy because it's part of human nature

It's not a man or a woman's job to make the other person happy only to try to live them the best you can and for

Both people's to due their duty for each other