In Japan, there's tremendous emphasis placed on personal upkeep and outward representation. Meaning that work culture is dominated by (what a westerner may perceive) as small and meaningless tasks; elaborate systems of greeting, proper grooming, wearing the right clothes, reorganising the drawers of your desk, copying important documents, and keeping your work space spic and span.
As an expat, it's important to pay attention to these little ideosyncracies and respect them, or in the very least, learn patience for them. It's easy to get frustrated when the act of picking out a tie supersedes the importance of putting together a final report.
In the end, the Japanese are productive, but over an unneccessarily long time.
As an expat navigating the work culture in Japan you'll also have to get used to the idea that business and pleasure are no longer separate spheres. Socialising with co-workers is EXPECTED, and getting completely debauched and throwing your name away for the evening is, in a weird way, respected. If you don't party with your colleagues you risk being perceived as a poor team player.