While riding on the subways, we noticed several people drinking a Sapporro. We also saw a lady walk through airport security with an open Sapporro and it didn't get confiscated. Needless to say, the Japanese are definitely much more laid back about drinking in public than the US.
We also saw beer vending machines, people having a beer in the parks, and to-go beer cups. So what's going on here?
I looked it on the internet and found several sites stating the same thing, and that a lot of people just don't mind it. Granted, drinking to excess or causing a disruption is probably going to draw some attention so there are limits, but I wasn't able to find out exactly what those limits were.