Amasake

Amazake is a traditional sweet, low-alcohol or non-alcoholic Japanese drink made from fermented rice. Amazake dates from the Kofun period, and it is mentioned in the Nihon Shoki. It is part of the family of traditional Japanese foods made using the koji mold Aspergillus oryzae (麹, kōji), which also includes miso, soy sauce, and sake. There are several recipes for amazake that have been used for hundreds of years. By a popular recipe, kōji is added to cooled whole grain rice causing enzymes to break down the carbohydrates into simpler unrefined sugars. As the mixture incubates, sweetness develops naturally. By another recipe, sake kasu is mixed with water and sugar is added.

Source: Wikipedia