Rice powder remaining on milled rice is carefully washed away. Then the rice is soaked for a length of time most ideal to achieve water saturation, which differs for each individual variety of rice stalk used. The degree of milling also determines the length of time rice must be soaked. The more polished the rice grain, the more it will absorb water, and therefore shorter the period of soaking.


Rice soaked to exacting precision is then steamed. The special process of steaming the rice grains leaves the outer surface of the grains relatively firm while the center is softened.


The steamed rice is then divided into those that will get sprinklings of KOJI mold and those that go straight into the fermentation process.