The University of Chicago Library's Map Collection includes gaihōzu 外邦図 (maps of the regions outside Japan, produced by Japan's Imperial Army during the era of the Japanese Empire.
How to search:
In the Library Catalog, select “map” for Format and type “rikugun” [army] in the search column; you will get:
"You could limit by date (approximately 1868-1945). You could exclude maps that had the word "japan" in the subject heading (although many of the topographic maps of Japan itself in this period were made by the same agencies). Also, there were several other military mapping agencies that made these maps, among them especially Rikuchi Sokuryōbu (陸地測量部) [it might work just to use "japan" as an author] plus some private companies like Minami Manshū Tetsudō Kabushiki Kaisha (南満州鐵道株式會社)." --Chris Winters