This means “Koji rice”. This is the white rice that is used to make Koji rice, or in other words, it is the rice that has the koji mold grown on it. This koji that is added to the main mash (moromi).
Bear in mind that the links to Tippsysake.com on this site are affiliate links and if you go through them to make a purchase I will earn a small commission. Keep in mind that I link to this company and their products because of their quality and not because of the commission we receive from your purchases. The decision is yours, and whether or not you decide to buy something is completely up to you.