Kōchi Prefecture comprises the southwestern part of the island of Shikoku, facing the Pacific Ocean. Shikoku is the smallest and least populated of the four main islands of the Japanese archipelago. Kōchi has a warm, humid climate with its annual rainfall the highest in the country except for Okinawa. It snows in the mountains, but generally it has fine days even in winter, although the temperature can drop to three degrees below zero at night, and there can be a large temperature changes during the day.
Kōchi is famous for its many rivers and the Mutemuka brewery is located close to the source of the Shimantogawa, Japan’s purest river. Founded in 1893, Mutemuka’s owner became a pioneer of organic farming when he refused to spray chemicals even against strong opposition from his neighbouring farmers. The regulations governing organic sake are extremely complicated. Each rice field must be certified organic which is a 3 year process of analysis and random inspections. After the field has been certified organic the rice can then be used for organic sake production, but inside the brewery additional regulations also apply to production, from what instruments are used to how the tanks are cleaned. All breweries wanting to be recognised as organic must also keep detailed records at all times. Organic rice paddies are generally less than half the density of regular fields so yields are about 50% lower and the production costs are generally 25% higher, so it takes a dedicated brewery to make organic sake. It is rare to see a brewery certified organic even if they practice the principles due to the lengthy and costly procedures, but Mutemuka Shuzō have become certified.