From around 1900, the population of the major cities, Tokyo especially, started to increase. The main drivers of this were the salaried workers, known as salarymen in Japan, who worked at government ministries and private companies. Living in the big city, their interests turning to Western culture, they were keen to try out new lifestyles. In particular, this salaryman demographic was fond of the preservative-free sake in bottles that brewers were releasing, enjoying a late-night drink at home.
This banner advert that would have been hung in train carriages probably around the start of the Taisho era, circa the mid 1910s, is advertising Gekkeikan Special Bottled Sake: Absolutely Free of Preservatives! The hand-written-style characters say Each bottle comes with the seal of the Osaka Hygiene Laboratory warranting it completely free of preservatives. To demonstrate this absolutely part, the sake was inspected by technicians at the Osaka Hygiene Laboratory and each bottle sealed by them before it was shipped.
The use of sake preservative (salicylic acid) was completely abolished after 1969, but Gekkeikan had already succeeded in developing and commercializing Japan's first preservative-free sake back in 1911. Since constructing the sake industry's first research institute in 1909, we had been busy working on scientifically understanding sterilization conditions and other bacteria-related issues. Until the start of the Showa period, in the mid-1920s, most of Japan's sake was still shipped in barrels and then sold by volume by the retailer. So Gekkeikan worked on commercializing sake that could guarantee its quality through having been bottled at the brewery.