Turn off the gas and leave any gas appliances unused. Do not forget about the ones that are put outside either. Make sure, too, that all unused gas taps are closed but do not turn off the gas meter.
Take off the cover of the reset button.
Press the button fully and release it. The button will come back up and the red lamp will start to flash. Then put the cover back on the button.
Wait for 3 minutes. Do not use any gas appliances for 3 minutes during which it checks whether there is any gas leaking. Check the gas meter after the 3 minutes and make sure the red lamp is no longer flashing. Then you can start using gas.

*If the red lamp still flashes after 3 minutes, there is a possibility of gas leaking or a gas tap not closed. Make sure that you turn off all of them, including your gas appliances.

*Caution
Start the procedure all over again when you turn off all your gas taps and appliances.

*Warning
If the red lamp still flashes even when you turn everything off, there is a possibility of gas leaking, so inform the closest Tokyo Gas office.