The following is a post about unions. If there are any non-Japanese nationals out there, who are teaching in Japan, I encourage you to find one, get in it, and stay in it throughout your tenure here. The reason I am writing this today is that we have officially started ours here at this school. Finally.
After ten years at Kumamoto Prefectural University, and all the discriminatory bile that we (my non-Japanese colleagues and I) were subject to, I moved to Yokkaichi, and now work in a great environment. You can read some of what happen at Debido Arudo's site. My experience here has renewed my faith in Japan. There are places where people are treated fairly. This, I am sorry to say, may be one of the minority, however.
If you are working or teaching at anywhere in Japan, you should join a union. The individual has far fewer rights here than a socially recognized group. This high context society is based on the group, not the individual. If you want to make any changes in your working environment, need protection, or just want a little insurance, join one today.
If you are not in a union and want to be in one, it is easy to join one that already exists, or you can make your own even if there is only one of you. Japan has some excellent labor laws, and if you are in a union or beginning the process, you are very well protected. It is the people who trust their employers to do the right thing that get called into the loading dock one morning to find that they will be out of a job the next day. It has happened. I have seen the victims and heard their tearful story, but since they were without a union, there was little anyone could do. The NUGW (National Union of General Workers) is a great group of dedicated, experienced people. They are used to working with non-Japanese, too.
Join a union. It is your constitutional right, guaranteed by the Japanese Constitution and United Nations treaties.