One more website which might be of interest to people looking for information on Japanese products, which was brought to my attention on the Japan Marketing News blog.
Japanese supermarket sales depend on supermarket circulars which come with daily newspapers. If you want to stick with the same product, but get it at the cheapest price, you are likely to have to keep up with the circulars and buy at a different store each week depending on where it is on sale.
I have read that this is why Walmart, through its Seiyu department stores in Japan, have not been able to get across the everyday low prices concept. Most Japanese shoppers, read housewives, still think about supermarket circulars first.
Here is a website where many of the supermarket circulars are reproduced.