The Ohara Institute for Social Research at Hosei University has an enormous collection of 20th century Japanese poster and propaganda art online: 2600 posters from before 1945, 400 posters of labor and social movements in the post-1945 period, posters and handbills from the 1930’s and an essay on the virbant history of the Japanese social movements between the two World Wars.
Found via coudal partners