For foreign workers in Japan, sometimes not being able to speak the language and unfamiliarity with the labor law leads to us being cheated. I am not an English Teacher in Japan , but just the same I am a foreign worker but in a different field. Being cheated is nothing new to me.
Some of might choose to remain silent and choose to fight for their rights. For English Teachers in Tokyo and maybe some other areas in Japan, here is a group/union that you can go to for assistance and information.