A word of advice

Do not come to Japan to "teach" English unless you have some other reason for being here. A year may be o.k. if you are interested in teaching as a career, but don't come and work for one of the big entertainment industry chain eikaiwa (conversation)schools. You will learn nothing except bad habits and have a good chance of being cheated out of money. You will deal with people of the most questionable ethics, and if you stay with it much you stand the chance of accepting and adoptingthe low standards and unethical. Dishonest behavior that is common in many of them.

Even teaching in good companies is not something you want to do long term if you don't have to. You can't really teach when you cannot test, when students won't do any outside class work, and won't write because they very mistakenly believe the only way to improve speaking is to sit around and shoot the shit.

The pay may seem good, but it isn't. It won't increase much over the long term. Companies like Berlitz rarely give annual raises and make a huge effort get you to pay for their responsibilties(e.g. Berlitz will often send "teachers" to different schools and refuse to reimburse them for the transportation costs.)

Again, do not make the mistake of coming here with an idea of a career in TESOL. Even in universities, if you have an MA in TESOL, my understanding is that you will have little actual input as an instructor, but simply expected to teach and shut the fuck up and let the brilliant Japanese staff make the decisions. After all, you are a happy boy airhead baka gaijin who could not possibly understand the Japanese or Japan.