In the next 4 to 5 days, the vat is filled with more water, more KOJI, and more rice. The batch is increased in 3 separate stages, with a day between each filling. With each filling, the batch doubles in volume.


Once the batch is complete, it is left to ferment for the next 18 to 32 days. The surrounding conditions such as temperature and vat size are exactly regulated to create the precise flavor.