Also bear in mind that the problems tourists encounter (not only language, but being unfamiliar with the train systems, credit card acceptance, foreign exchange, etc...) are usually short-term problems. To these, the person living here will have to add problems like difficulty getting home loans, job security, residence and taxation issues, funding of retirement, separation from aging parents, etc... Many of these are problems of adulthood no matter where you live, but they can be complicated by living overseas. There are also things like loss or degradation of some legal rights, and other serious issues like how you will raise your kids if you decide to get married in Japan.
Heavy issues, for sure, but its important to realize that life in Japan is not all tea-ceremonies and zen gardens. The bright side is that despite all of the above, a lot of people manage to build quite good lives here.