Based on your post, I assume you are moving (or contemplating a move to Tokyo (if so, welcome to Tokyo) rather than the west of Japan. In that case, the frequency is 50Hz, same as France. These guys
have a product which is supposed to be a self-regulating step-up/down transformer (100V to 220V input, 100V-230V output).
There is one available here
on Yahoo! Auctions (the Japanese version of eBay), offered at JPY 90,000, which should translate to about 750 euro. It may be cheaper if ordered directly from HK but i could not get the HK site to work well on my browser. The mfr. asks that it be set up by a licensed electrician, but it looks like it would probably serve your purposes.
Otherwise, the premier Japanese mfr of products which are like PS Audio's is called CSE, and their product just does step-up from 100V to 117V. Accuphase's offerings are just waveform regenerators - no step-up.
Otherwise, Japan has a very active market in used equipment on the Yahoo Auctions, in high-end stores, and on HiFiDo (www.hifido.jp). You may find it interesting to explore what Japan has to offer while you are here. If you are at all a DIYer, there is actually a strong used market for well-built DIY tube equipment and one can buy, experiment, and sell for very little friction (and if one is good/careful, one will sell for a bit more than one bought).