How the Nova System Works for Teachers:
Nova's source of income is not only it's customer's but also its employees. The average employee does not speak the language, know the law, and in most cases has very little experience with work and living in a foreign country. Making them perfect canditates for exploitation, abuse and all round victims of corporate sodomy.
This act can continue for about a year, sometimes longer. But don't worry once the employee wisens up, it'll be too late and they will have had enough and leave.
see also: Let's Japan.org - 'To Hell With Nova'