Have you been to Japan before? (I assume, since you're moving there) The plugs are the same as here just less voltage capacity and no grounding part. (but it also depends on where in Japan you're living) Radio Shack and other electronics places sell mini battery back-up/surge protectors/power cords -- but your best bet will probably be to buy that sort of thing when you get to Japan to make sure you don't blow the circuits in your new place. Also talk to your landlord/apartment head/whoever about the building ---they would know the best about what works and what doesn't.

The power converters they sell in Japan are designed for Japanese electronics used overseas. It is extremely difficult to find converters for foreign electronics, one of the problems being that voltage is LOWER in Japan than abroad (100V, 50Hz). While foreign laptops & other battery-based electronics will work just fine, things like clocks & hair driers won't. You will need to get a voltage converter that can step 100V up to 150V. It will be easier to find one of these (and probably cheaper) outside of Japan.