Electric current in Japan is 100 volts and uses two different frequencies per region:

For Kansai and the east region of the country 50Hz For Kanto and North region of the country 60Hz

Japanese plugs are type A ungrounded plug with two flat parallel pins. If you are visiting Japan soon and your gadgets have the same plug, you won’t be needing any adapters.

In case your gadgets have different type of plugs you can readily buy an adapter easily. You can find one from the airport stores and from tech stores which is all over Japan especially in Akihabara.