It's very tasty, with a soft mouthfeel, a delicious taste of rice, and a good acidity. It seems to be sold only in the direct sales area, but it is worth going to buy.
This is an old-fashioned doburoku. According to the brewer, it is made by Yamahai brewing. The alcohol is 12%, and the sourness and sweetness are exquisite. It is a mixture between yogurt and amazake. The grains of rice that remain in the glass are delicious.
100% Koshihikari rice from Sado Island. I wonder if this is what they used to drink in old Japan, before sake was invented.