Edit: Just to clarify - this isn't a drinking game. I rarely (if ever) play drinking games. I presented it as a game because it seems to me that there are rules that everyone unknowingly follows. In reality, the way people act comes out of respect for each other and is in keeping with the social atmosphere. Eating and drinking is a huge part of the social culture in Japan; there are always people who take things too far, but in general, the drinking is just a social activity, and kept to a reasonable limit. It's not used as an excuse to drink excessively or act inappropriately. Please read with this in mind. :)
It's like a contest. Or a game - with elements of quickdraw and musical chairs.
Round 1 - If a beer glass should be emptied - even ever so slightly - a player must immediately reach for the closest beer bottle to refill it. Once a hand has picked up a beer bottle, the remainder of the players ought to quickly grab for one - as there are not quite enough to go around.
Round 2 - Upon filling the glasses of everyone around them to the brim, players may set down their beer bottle, and - accompanied by 'Sumasen', 'Arigato', and bowing - may lift and tilt their own glass to be filled.
Round 3 - Short break. Conversation continues.
Round 4 - Someone takes a sip. Repeat from Round 1.
Ending the game - The Game can only be ended when the collective group leaves the establishment. At no time during or after dinner, while seated in the restaurant, should players cease to participate.
You think I'm exaggerating. But I'm not. Last night was a goodbye party for our team manager, who received a promotion and will be working out of a different office. I spent the first few minutes of dinner just watching the Game. It made me laugh. Often, when the glass was still full to a centimeter (a centimeter!) from the top, someone would pour to refill it. Then the person who's cup was filled quickly picked up the beer bottle to return the favor. And then everyone else jumped in - rushing to make sure everyone's glass was full to the brim. It was quite amusing to watch, and difficult to describe so as to give you a sense of the urgency with which it was carried out.
After dinner, 7 of us continued the party at a karaoke bar the next station over. We sang, drank, and laughed our way to 12:30. At 12:30, we finally wrapped it up to head home. Having missed the last trains, we taxied home - I shared a cab with Takemori-San and Matsushita-San. I can't even imagine how much the evening must have cost. Dinner was high-class, and everyone (17 people) had at least 3 drinks plus infinite amounts of beer. I'm sure you could fill a bathtub with the empty beer bottles. The karoake bar included several more drinks and snacks, for 7 people. Our taxi meter was at $55 when they dropped me off - with two more people to drop off. A second taxi took home the rest of the group. Eating and drinking with coworkers is a huge part of culture in Japan - but I'm still amazed at how much they so often invest in it.
So - I had a great night, lots of fun, 5 1/2 hours of sleep...hehe. But it was fun to hang out with my coworkers outside of the office.