Rarely as a Japanese businessman can you quit a job and find another job at either the same or higher pay grade.

The market here revolves around hiring university graduates up to a year before they graduate and then training them from the start in whatever position you want them to do. Very few people change jobs and if you jump from jobs every 3-5 years its seen a negative sign on your CV.

I think it's more cultural than efficient. Working more than 60 hours for most people results in no added outputs.