This study offers a social-historical analysis of the “Russian flu” pandemic in Japan (1889–1891). Due to scarce statistical data, the study relies primarily on contemporary newspapers and magazines. It identifies two distinct epidemic waves: the first in spring-summer 1890, and the second from late 1890 to spring 1891. The first wave, though widespread, was overshadowed by a concurrent cholera epidemic and caused relatively few deaths, whereas the second wave was far more lethal and generated widespread fear. At the time, influenza remained an “unknown disease”, with unclear etiology and no established treatments. People responded with diverse measures, from purchasing patent medicines and using folk remedies to symbolic practices such as "disease naming" (osome-kaze). The crisis also renewed attention to historical records of earlier influenza-like epidemics in Japan. In contrast, by the time of the later “Spanish flu” pandemic, advances in bacteriology had already rendered influenza a medically defined disease. This comparison highlights how shifting medical knowledge shaped societal responses. The findings not only corroborate previous excess-mortality analyses but also provide new historical insights into how societies have historically confronted pandemics.