Most people would sleep more easily if they felt safe and were not on high alert for danger. So from that point of view, falling asleep might show confidence in the other people present and that would be a compliment to them.
As for me, I have never fallen asleep in a gathering. I don't even sleep that well at night--and I don't even have guilty conscience, nor am I anxious.
As for the Japanese: I was extremely favorably impressed by them when I was there in 1974. They were hard workers and I never detected any hostility toward me. In fact, we were there during a school holiday and I was approached by many students wanting to shake hands and test their English and also to take my picture. Usually tourists take photos of the natives, but here, the natives were taking photos of the tourists. Also, every space was tastefully utilized. There were crowds and they even had "pushers" to get the last passengers into the bullet trains, but somehow I didn't feel overwhelmed by people (I am almost never overwhelmed). D.W. Bales