[jasonbvr]

No one is going to crucify you, but you will get a lot of stares and probably find people to be a bit apprehensive about the two of you.

Let me give you a real example, I took some foreign friends to a darts bar one night and they were having a final round to their tournament. They shut the music off and everyone in the place was being quiet. I wasn't even sitting with my friends because I was trying to watch the game. My friends are your typical loud American types and were just talking the whole time. No one got mad or anything, in fact they were fairly well ignored, but I still felt embarrassed. Now if I go to a bar with these same friends and there is a group of extremely loud Japanese businessmen getting hammered sitting at the table next to us, no problem.

Point of the story is, Japanese are polite enough to tolerate your friend's ignorant behavior. The one who is likely to be embarassed or bothered by it is probably going to be you.