In general, entertaining guests in the Japanese domicile is unspokenly discouraged (unless its a quiet affair) because of the density of the Japanese population, the thickness (or lack thereof) of the walls, the general belief that any and all disturbing activities should be limited so as not to inconvenience your neighbours, and so on. By entertaining I mean celebrating something, drinking, talking loudly and enjoying oneself, karaoke, etc.
Izakayas, karaoke dens and clubs are open very late in order to provide places for people to let loose, drink and make some noise. That being said, it really depends on who's around. The izakaya I frequented most during my time in Japan was absolutely churchmouse-quiet at times, and at other times the smoke was so thick in the air and the noise was so intense it was almost too much even for a seasoned Westerner. It's just a matter of who's celebrating and how much drinking is going on. In situations like this it's perfectly acceptable to be loud provided its an izakaya or a bar suited for these purposes.
As was pointed out, fine dining establishments are usually off-limits for this kind of thing. However you'll still get the occasional group of salarymen or businsess trippers who turn the bar or back-room area upside down before last train. This is also usually acceptable up to a certain point.
As an aside, one time after finishing a meal at the local yaki niku (Gyu Kaku! mmm..) my friend commented that the table beside us had been rather loud and intrusive, choosing to practice their English as loudly and drunkenly as possible. The location was generally a quiet-ish one, not a regular party destination. I noticed several looks of disapproval from other Japanese patrons. She made the comment jokingly but the server at the counter gave her some valuable coupons and extra candy as an apology.