Koji is steamed rice that has had koji-kin, or koji mold spores, cultivated onto it. This magical mold, for which the official scientific name is Aspergillus Oryzae, creates several enzymes as it propagates. These enzymes break down the starches in rice into sugars that can be fermented by the yeast cells, which then produce alcohol and carbon dioxide. Without koji, there is no saké. And our Toji, Jeff, grows it right here in the kura!