Before coming to teach in Japan, people should have some kind of warning... Caution: your individual experiences may lead you to make an over-reaching generalisation about life in Japan, when reality may actually be quite different.
It’s always best to keep an open mind when you immerse yourself in another culture. That’s a guaranteed way to reduce culture shock in the long run. However, just because you are told something is true before coming to or during the beginning of your time in Japan, it doesn’t make it so.
For example, well into a conversation about public and private elementary schools in Japan, I became aware that an acquaintance of mine was completely misunderstanding the term “private school” because the staff at an English conversation school where he originally worked referred to themselves in that way. Trust me, there is nothing at all similar between a Japanese private school (私立学校 shiritsu gakko) and an English conversation school (eikaiwa 英会話), let alone a cram school (juku 塾) or a language school (senmon gakko 専門学校). According to some people, all of these are called "private schools". This can cause quite a gap in communication.
Another similar example involves a name many people may already be familiar with. There are several ways to come to Japan for the first time in order to start your career in teaching English abroad, and one of those ways is via the famous JET Programme.
The starting salary for a position there can be over 3 million yen a year, and rise up to 4 million yen or more by the third-fifth years. That starting salary is a lot more than what 'real licensed teachers' get in their first year of teaching. As for what the final years with JET offers, those pay scales are well above average, considering 'only' 3-5 years of teaching experience and getting the job by merely being a tertiary educated native English speaker.
A common problem occurs when former JET teachers start looking for a new position with even higher pay, completely oblivious to the fact that what they were receiving before was actually not normal at all. That experience gave them false conceptions about how pay scales work for English teaching jobs in Japan. It can be a harsh drop back to reality.
If you're really determined to get that upper end of a pay scale as an English teacher in Japan, you'd better be sure that you at least have a teaching license from your home country, some years of experience as a 'real' teacher. A Masters degree in a field related to teaching or language arts would help, too. Oh, and you'd best just apply to IB international schools!
The general advice is to always keep an open mind, do plenty of research, talk with lots of other English teachers, and never set your generalisations in stone. They need the flexibility to shrink or expand with your next new experience abroad. That way, you can be sure not to become like this guy.