Hi Justine, I work at a small college and really enjoy it. I’ve only worked at one language school in Hiroshima. It is pretty famous and based only in that area. Also with a Master’s degree, this school might be able to get you some university/college classes. To be honest, the language school thing didn’t suit me, but we all have different expectations and most of the people I worked with thought that particular school was one of the better ones.
Most people I know in the language school business prefer to find smaller schools, but I’ve heard many of those don’t want to do the initial visa sponsorship anymore and generally look for people who are already here.
You might also consider the ALT (assistant language teacher) companies. I’ve heard good things about some of them, especially if you are interested in working with kids.
Once you are here and have some experience/connections, you might be able to find part time college or university work even though your Master’s degree isn’t in teaching English or linguistics.
Like Ali said, please feel free to PM me if you have specific questions about different companies or schools.
Hope this helps
Wendy