Compatibility summary
You will need a travel adapter in Japan; plug types used there differ from France. Voltage differs by more than 20% — a voltage converter may be needed for some appliances.
Plug comparison
France plug types: C E
Japan plug types: A B
There is no common plug type between France (C E) and Japan (A B). You need a travel adapter.
Voltage comparison
France: 230V, 50Hz
Japan: 100V, 50Hz
Voltage converter recommended (France 230V vs Japan 100V).