Here is some recent commentary from the Osaka General Union.
The union has people asking the hypothetical, “what happens to my job after five years?” The reality is, I believe, that most employment contracts presented to foreigners have so many illegalities and loopholes within them, that very few foreigners last the five years.
(As an example: thirty day notice provisions in supposedly “fixed term” employment contracts. Patently illegal in Japan.)
Are there foreigners in Japan who have been working, in perma-temp status, under a series of contracts for five years? Yes. Does this modification to the law make it more likely that some foreign workers will be shown the door before Year Five? Yes. Right?
The larger issue is the number of times that foreigners who obtain regular employment status, under Japanese labor law, later have that denied—through one trick or another. People being perma-temped under a series of fixed-term contracts have a target on their back anyway, same as those whose sei sha’in status in the law is not recognized.