There is a huge drinking culture in Japan, and Tokyo has countless number of bars in all areas. Many of these places are open way past the trains stop running, so it’s not unusual to go to 2-3 different places during the course of a long night. The first stop is called “一次会” (ichijikai), the second is “二次会” (nijikai), and so on. I’ve had friends say they go all the way up to 五次会 (5th bar!), but 3 is usually the limit for a long-ish night.
It’s always fun going out with coworkers for the night. The first place you usually are tends to be a normal restaurant. You enjoy some drinks and food, things are fun. A couple of drinks in, and this guy in your group says he knows a place near here that has good music. You pick up the bill, and head over to the next place in good spirits.
However during the blur of the night, the 3rd or 4th places you end up at are more than likely some sort of weird specialty bar with some weird theme and weird cocktails you really don’t want to drink.
Think of these sorts of nights as character building exercises. Enjoy seeing your normally silent coworkers singing “Linda Linda” in unison and attempting to breakdance. The dichotomy between day and night for a salaryman is truly fascinating.