I had an office in the Hanzomon area of Tokyo that had a deck that looked across the street into an engineering firm. Yes, the workers were there from 8AM-6 or 7PM every single day (including the ubiquitous half-day Saturdays). HOWEVER... 9 times out of ten when I went out on the deck to smoke a good portion of them were staring into space, slumped in their chairs, or outright napping. Sure, they worked long hours but I highly doubt they were any more productive than workers nearly anywhere else in the world. That's not to say the Japanese are not industrious... rather that the image of the busy-bee worker putting in long hours is more important than the actual output.