Mix well, cover and leave at room temperature for about a week. On the following day, stir the mixture once a day with a clean spoon.
After some time, the koji may absorb the Shoyu content so please add appropriate amount of Shoyu until it covers the surface of the koji completely. The amount of Shoyu absorbed depends on how dry the koji is, so observe the condition of the ingredients and replenish Shoyu where necessary.
After about a week, the solution becomes thick. This signals that Shoyu Koji is ready for use. In the colder months, this process may take 10 days to a week.
Please store Shoyu koji in the refrigerator when completed. The standard storage period is about 3 months.