If you are planning a visit to Japan, short or long term, and intend to drive, then yes you will need an international driving permit. Even if you don't plan to, if you just want to be able to drive should the chance arise, you will need it and the low cost versus the convenience means it's worth getting.

If you haven't been to any Asian countries yet, you may not have come across a squatty potty, but if you have been in Japan then you probably have. Here's a quick how to on squatty potties.

In Japan, battery sizes don't follow the battery size name conventions you might be used to if you come from an English speaking country.