Kingyozake is a familiar name of sake which is so weak that a kingyo (goldfish) can swim in it.
The Sino-Japanese war began in 1937, when the production volume of sake decreased due to rice deficit. The rationing system of rice, material of sake, was implemented to sake breweries as well. The half of the sake breweries throughout the country were forced to go out of business by Sake Producing Equipment Instructions in 1943 as a national policy during the war time. Furthermore, from that time, sake breweries were placed under the strict control of the National Tax Agency, and the tax on sake brewing had a system that more water added in the finished sake, the cheaper the tax became. The decrease of production volume of sake due to the deficit of rice, its material, and closing of sake breweries caused water-adding happened in sequence during the course of distribution; sake breweries, wholesalers, retailers, and consumers. As a result, the sake which was so weak as to be called Kingyozake was marketed.