There was a very interesting article in the 2008.5.21 issue of Nikkei Shimbun (Japanese edition). It lists the tariffs on the importation of several basic food items.
Polished Rice (コメ、精米) 341 yen per kg (resulting in a 788% tariff at current prices)
Wheat (小麦) 55 yen per kg (252% tariff)
Beans (小豆) 354 yen per kg (402% tariff)
Sugar (粗糖) 71.8 yen per kg (305% tariff)
Butter (バター) 29.8% of price + 985 yen per kg (360% tariff)
Cheese (チーズ) 29.8% of price (29.8% tariff)
It does not take a close analysis of the data to see two things:
1) what food items Japan already produces and wants to protect, or put another way, what items Japan believes it can have a degree of self-sufficiency in,
2) why there is no butter on store shelves, but cheese is still easy to find. In the article, it states that Japan has a goal of being 90% self-sufficient in butter. Demand was misjudged several years ago (when such things need to be planned for) and now there is no quick fix. World prices have sky rocketed and to that price an additional 360% is added, which results in it being very difficult to import butter to make up the difference.