[mochaccino]

Yes, it's illegal but it happens more than most people think, even in the US. The FDA does not test supplements unless it gets reports of adverse events that can be directly linked to a product. That means that there is absolutely nothing stopping manufacturers from padding their supplement with drugs, other than possibly the fear that an adverse event, or several, will somehow be linked to the supplement and cause them to be reported to the FDA. Apparently, 400 products have been taken off the market by the FDA since 2008 for containing undeclared drugs. Im sure that is only a small percentage of the supplements that actually contain drugs. Just to give you a better idea of how common it is for certain categories of supplements to contain drugs, check out this article about popular herbal and glandular thyroid supplements: http://www.m.webmd.com/women/news/20111028/study-thyroid-support-supplements-may-be-risky

It may seem weird that Im talking about the US instead of Japan, but I seriously doubt that Japan is much different. It would take extraordinarily strict, draconian supplement laws in order for a country to directly test every supplement that comes to market. They would need to very severely limit the number of different kinds of supplements that can be sold, and the number of manufacturers that can produce them. The very fact that Japan has such a booming supplement industry, with a huge number of different brands available, proves that the Japanes government can't possibly be testing supplements. At best, they probably monitor reported adverse events, like the US does.