Yeah....companies do all sorts of "favors" for their employees. There is a possibility that an examination of the facts might reveal this to be a case of wrongful termination. Companies are allowed to restructure employees out the door if they can show a need to do so. Whether this is such a case or whether they're just trying to have you all do the same work for less pay and under less favorable terms is something beyond our ability to judge.
Talk to a labor attorney. The local bar association can recommend someone and may even have "first time free" consultations available. Your local city hall may have such service available especially for foreigners. You may also find it worthwhile to consult with the Labor Standards office (労働基準局).
Get informed opinions from knowledgeable, trained, qualified, practicing professionals who actually know what they're talking about and may actually be able to help you in a meaningful way. Well-intentioned strangers on net forums are good sources of sympathy, but little more.