The origins of sake date back to ancient Japan, with the earliest references to rice-based fermentation appearing as early as the Nara period (710–794). At this time, rice was considered sacred, and its fermentation was believed to have spiritual significance. The first versions of sake were made in a rudimentary way, often involving the fermentation of rice with naturally occurring molds and yeasts, a process known as "kōji" fermentation.
During the Heian period (794–1185), sake brewing became more refined. The practice of using a special mold, known as Aspergillus oryzae, to break down starches in the rice into sugars, which could then be fermented into alcohol, was developed. This is the technique still used in modern sake brewing today. The quality of sake also improved as techniques for selecting high-quality rice, controlling fermentation temperatures, and filtering the sake were honed.