Brief overview of "Pre-War Price" statistics:

Both the Tokyo Retail Price Index and the Tokyo Wholesale Price Index were compiled and published by the Bank of Japan. For details, please see the website of the Institute of Monetary and Economic Studies, Bank of Japan

Both indices show that prices in Tokyo went through a prolonged deflation between 1920 to 1931, with a particularly violent decline in the last two years between 1929 to 1931. Prices bottomed in 1931 and a moderate inflation followed for several years, until double digits inflation took over after 1937-1940.