Quitting certainly is the ethical thing to do. I wonder if I'd quit if I was in their position.
Handing your concerns to management in writing isn't really a done thing in this culture. I sometimes get laughed at for even suggesting it. And people who quit often take a massive pay cut, are forced into contract work with no safety, or even don't ever get hired in software again - especially in Nagoya where everyone seems to knows everyone.
And when you have a family and a mortgage to pay (selling a house here is also a guaranteed massive loss), it can realistically be a choice between you and your family on the street or doing what you're told.
While the engineers aren't blameless, the system over here is really broken.
