To brew sake rice, koji and water are used. After this brew is ready, the sake is pressed and the liquid (sake) part is separated from the solid parts, called the sake kasu. This sake kasu has been used from early times to pickle fish and vegetables. Soups are also made with it and also Wasabi Zuke (pickled wasabi).
When the Sake Kasu has just been pressed, it is white in color. Over time, it will turn brown and acquire a fuller flavor. Know that sake kasu still contains a lot of the koji mold and is therefore "alive".
Since 1988, Moriki Shuzō has produced only junmaishu, pure sake that is made only with rice, kōji, and water, without any added alcohol.
They also grow their own rice. They don't use herbicides and pesticides, they force the rice to rely on its own natural tendency to protect itself from weeds and insects, thus bringing out the full potential of the rice to grow vigorous, hardy grains. The only fertilizer they use is sake kasu.