Part of the sakura season in Tokyo is the celebration; gathering friends, throwing down a blanket on the grass and hanging out. This usually involves food and of course – drink.
It gets very crowded under those trees.
I cannot see what the sign on the left says but I think it says that you are not allowed to have food there.
Public alcohol is not a problem in Tokyo, it would appear. This shot (above) was taken at Arisugawa park. A beautiful park near Hiroo station in the heart of Tokyo.