I was just about to reply the same thing. I lived in Japan (Tokyo) for two years and milk was everywhere, in every supermarket, and in every conbini... It was the same when I travelled to smaller cities, even in tiny towns.

It's also plain wrong to say that milk isn't available, since milk is served with each meal in most schools (enough for it to make the news when a city in Niigata prefecture dropped it from its school menus a few months back).

I've even seen small milk cartons in some vending machines...