I forgot to mention: When you see "related agencies" like that, it's often the case that one is used for the teachers with the right credentials who can obtain a Z visa and where the school has the right to hire foreign teachers: the "good" agency. And the other agency, the "bad agency", is used for teachers who do not qualify or for schools that can't hire foreign teachers. In this way, it appears that the left hand does not know what the right hand is doing. The danger for the "good" agency is that a crackdown on the "bad" agency would cause big problems to the common owners, and the foreign teachers related to the "good" agency can find themselves without a contract to enforce, without pay if it is the agency that pays the teachers, without any help in case the teachers have a serious problem.