In the occurrence of spillages on your Tatami, here are the steps you may take:

Using a dry cloth, add a considerable amount of pressure onto the spillage area to soak up any excess liquids.

Add half a capful of Dettol i.e. antiseptic wash, to half a pail (i.e. 1500 ml) of water. Rinse a clean cloth within this solution and proceed to wipe the affected area of your Tatami. Make sure the cloth has been squeezed dry before wiping.

If the spillage leaves behind an odor:
Add 3 tablespoons of white vinegar to half a pail (i.e. 1500 ml) of water instead.

Direct the air-flow of an electric fan onto the cleaned spillage area for at least 45 minutes. The affected Tatami may also be taken out to sun for 15 minutes.