Most of the folks who take these positions end up leaving Japan very disappointed or sitting in the Union Offices listening aghast as they learn of the snow job for which they fell. 15 contact hours will be tiring after three or four months when the novelty wears off. You do not want anymore. Furnished is often a ploy to make you think it is furnished. It is usually a futon and that is it.
Phone can be really expensive.
Mandated by law. Not their idea. You will need to fly back within a predetermined time. Usually the default period which is two weeks after the job finishes. Mandated by law.