Compatibility summary
Your Japan plug may fit in Montserrat outlets, as both use at least one common plug type. Voltage differs by more than 20% — a voltage converter may be needed for some appliances.
Plug comparison
Japan plug types: A B
Montserrat plug types: A B G
Both countries share at least one plug type (A B and A B G), so some plugs may work without an adapter. Check your appliance.
Voltage comparison
Japan: 100V, 50Hz
Montserrat: 230V, 60Hz
Voltage converter recommended (Japan 100V vs Montserrat 230V).