Tomizu refers to the 10:10 ratio of rice to water used towards the end of the Edo era. Yamagatas Haenuki sake rice, well water sourced from Mount Gassan and local Yamagata NF-KA yeast composes a thick fermentation mash that they mix using their own invention called an OS Tank. The resulting texture is minerally and thick but with kire, a clean finish, and a wonderfully restrained aroma.