Toto toilets are high efficiency toilets and as such have a different flush valve than is on standard toilet. The most common flush valves used on a Toto high-efficiency toilet is either the Lavelle #528T or the Korky #528 QuietFill valve. The flush valve controls the flow of water into the tank after flushing and shuts off the water when the tank reaches the desired level. The flush valve can be adjusted so it allows more or less water into the tank before it shuts off.
Turn off the water supply to the toilet by turning the shut-off underneath the toilet all the way to the right. Some toilets may not have a shut-off, and so you will have to shut off the water supply by turning off the main water shut-off for the entire house.
Flush the toilet to get most of the water out of the tank.
Turn the upper half of the valve counter-clockwise to unlock it.
Pull the upper half of the valve up until the water line on the valve is level with the water line on the tank.
Turn the valve clockwise until it snaps into place. Turn on the water supply.