"Working as I do in a large company in Japan"
I would assume that SALARY employees don't get overtime pay in Japan, either?
in which case, the boss's paycheck won't be affected if you deduct overtime pay from his pay [because there won't be an overtime bonus for the employees staying late to finish up or whatever].
Also, is it that competitive for well-paying jobs in Japan, that people are COMPELLED to look like they're working harder/better/faster than everyone else? Just curious.