No, even many high-level businessmen worked 12-hour days. It was partly to show how diligent they are, and partly to show their loyalty to the company.
The thing is, it's not so much "working" for 12 hours, but simply staying at the office for 12 hours -- give or take a few hours.
In one office I worked in, the workers would sit around in the office, past 6 p.m., past 7 p.m., often doing work that could easily be delayed until tomorrow, or sometimes, even pretending to do work. Finally, at 7:30 or 8:00 p.m., the manager would say, "Tanaka san, you can go home now."
It was insane.
damn.. thank you then for the information about japan while you been there sir...