Non-polarized Plug
This type of electric plug will fit any power outlet in Japan.
Polarized Plug
This type of plug will work fine at most places. However, it is possible to find some non-polarized power outlets in Japan.
Grounded Plug
Because of the ground pin, this type of plug will not fit any power outlets in Japan. You will need an adapter to make it work.
Device Compatibility
If your electrical product indicates the power input as 100V and 50-60Hz, it will work normally without a power converter. Most of latest computers, iPods, and battery chargers are compatible with Japanese power system.
Frequency of Electricity in Japan
The frequency of electric current is 50 Hertz in Eastern Japan (including Tokyo, Yokohama, Tohoku, Hokkaido) and 60 Hertz in Western Japan (including Nagoya, Osaka, Kyoto, Hiroshima, Shikoku, Kyushu), however this frequency difference affects only sensitive equipment.