Continuing with the Nikkei Style article on the history of sake, wet-field cultivation of rice reached Japan between the Jomon (14,000 - 300 BC) and Yayoi (300 BC - 300 AD) periods.
Fermentation could have been first discovered in the Kyushu and Kinki areas when heated grains were chewed, mixed with enzymes (diastases) in the saliva, and then exposed to ambient yeasts that turned the sugars created by diastases into alcohol.
Even the verb kamosu (醸す), to brew, seems to have come from the verb kamu (噛む), to chew. Although raw materials with natural sugars, such as grapes or honey, would ferment naturally given the right conditions, humanity lacked the knowledge and techniques to ferment grains.
The ancient quasi-mythical text Kojiki also records a visit by the Korean noble Susukori from Paekche, the ancient capital of Korea, at the start of the Nara period (710 - 794 AD). He brought with him alcohol produced using kōji, and this brewing method then became established in Japan. The Japanese government set up an organisation called Miki-no-tsukasa or Sake-no-tsukasa (酒造司) dedicated to making sake and other fermented products.
In the Heian period (794 - 1185 AD) temples such as those on Mount Koya produced a style of sake known as sōbōshu (僧坊酒, Buddhist temple/monastery alcohol). Both rice and sake continued to be economically important commodities through the Heian, Kamakura (1185 - 1333 AD) and Muromachi (1336 - 1573 AD) periods. Breweries such as Yanagizakaya (柳酒屋, Willow brewery) and Umezakaya (梅酒屋, Plum brewery) started to appear around Kyoto.
The Goshu-no-nikki (御酒之日記, diary of alcohol), written around the beginning of the Muromachi period, has detailed descriptions of a two-stage build of a fermented product made with kōji, steamed rice and water, together with lactic acid fermentation and the use of charcoal, showing that the modern methods of producing sake were more of less in place.
Other technical developments, such as the ability to build large wooden vats, also contributed to modern-style brewing by making brewing in larger volumes possible. The Goshu-no-nikki also mentions distillation and the production of shōchū.