Voting certificate, Muramasa; WikiMedia Commons.

The General Election Law of 1925  extended suffrage to all Japanese males aged 25 and over.

Since the Meiji Period of imperial restoration began in 1868, the Japanese government had been suspicious of democracy. Limited suffrage was allowed only for tax-paying male property holders over age 25 (roughly 1% of the population). 

After WWI, popular movements arose to eliminate the tax-paying requirement. With increasing student and labor demonstrations, and popular press coverage, the government was moved to provide universal male suffrage.