A list of open access primary sources for the study of modern Japanese history, with a
searchable database of digitized books. Aimed primarily at students working with sources in Western
languages. Choose a heading to open it. See also:
Millard's Review 1917-1940 - Changed names several times. Also a China-based periodical but also frequently has articles related to Japan and Japanese imperialism.
Your first stop should be the Digital Resources and Projects on East Asia by Paula R. Curtis. There is an extensive table there which can be filtered by time period and area, among other things.
Global Politics on Screen - Website dedicated to the Japanese film "Investigation of the Lord Lytton Mission into the Manchurian Incident" on the 1932 Lytton Commision.