The voltage of electricity in 100V in Japan. The frequency is 50Hz in Tokyo. Inthe western are in Japan, for exaple Osaka and Kyoto, the frequency is 60Hz.
The shape of the plugs are shown above. Normally they are ungrounded with two pins. However The plug with two pins and a ground pin is often used for PC.
In many cases equipments from other countries might not work or even get damaged. It's better to bring a convertor to use your equipments in Japan.