These links are all to the Japanese National Diet Library Digital Collection public archive and are freely downloadable (no intelectual property it seems). If it is against the forum rules, then i hope moderators will be gentle.
IJA Aircraft manuals:
Mitsubishi Ki-1:
Manual for operating Type 93, heavy bomber model No. 2 with drawings prepared by Army Air headquarters, May 1935.
Manual for operating Type 93, heavy bomber model No. 2 with drawings prepared by Army Air headquarters, May 1935. Report No. 15n(1), USSBS Index Section 2 - 国立国会図書館デジタルコレクション
Nakajima Ki-4:
Manual for operating Type 94, reconnaissance plane with drawings prepared by Army Air headquarters. May 1937(revised).
Manual for operating Type 94, reconnaissance plane with drawings prepared by Army Air headquarters. May 1937(revised). Report No. 15n(4), USSBS Index Section 2 - 国立国会図書館デジタルコレクション
Tachikawa Ki-9:
Manual for operating Type 95 (Model 1B), training plane with drawings prepared by Army Air headquarters, November 1938.
Manual for operating Type 95 (Model 1B), training plane with drawings prepared by Army Air headquarters, November 1938. Report No. 15n(5), USSBS Index Section 2 - 国立国会図書館デジタルコレクション
Mitsubishi Ki-15 II:
Manual for operating Type 97, headquarters, reconnaissance plane (Model No. 2) with drawings prepared by Army Air headquarters, March 1941.
Manual for operating Type 97, headquarters, reconnaissance plane (Model No. 2) with drawings prepared by Army Air headquarters, March 1941. Report No. 15n(9), USSBS Index Section 2 - NDL Digital Collections
Mitsubishi Ki-21 IIa:
Manual for operating Type 97 (Model No. 2), heavy bomber with drawings prepared by Army Air headquarters, October 1941.
http://dl.ndl.go.jp/info:ndljp/pid/8815752
Kawasaki Ki-32:
Manual for operating Type 98, light bomber with drawings prepared by Army Air headquarters, September 1939.
http://dl.ndl.go.jp/info:ndljp/pid/8815748
Tachikawa Ki-36:
Manual for operating Type 98, direct cooperation plane with drawings prepared by Army Air headquarters, August 1940.
http://dl.ndl.go.jp/info:ndljp/pid/8815745
Nakajima Ki-43:
Manual for operating Type 1, fighter plane, with drawings prepared by Army Air headquarters, January 1942.
http://dl.ndl.go.jp/info:ndljp/pid/8815753
Oxygen inspirator for Type 1 (Model 3), fighter, April 1945, Army Air Inspector General.
http://dl.ndl.go.jp/info:ndljp/pid/8815780
Mitsubishi Ki-46:
Oxygen inspirator for Type 100, headquarters reconnaissance plane (Model 3 and 4), by Army Air Inspector General(two copies).
https://dl.ndl.go.jp/info:ndljp/pid/8815783
Kawaski Ki-48:
Manual for operating Type 99 (Models 1 and 2), twin-engined light bomber, published by Tokorozawa Army Air Maintenance school, October 1944.
http://dl.ndl.go.jp/info:ndljp/pid/8815754
Nakajima Ki-49:
Manual for operating Type 100, heavy bomber with drawings by Army Air headquarters, August 1941.
http://dl.ndl.go.jp/info:ndljp/pid/8815751
Mitsubishi Ki-51:
Manual for operating Type 99, Army reconnaissance and Type 99 Army assault plane with drawings prepared by Army Air headquarters, March 1941.
https://dl.ndl.go.jp/info:ndljp/pid/8815749
Mitsubishi Ki-67:
Oxygen inspirator for Type 4, heavy bomber, March 1940, by Army Air Inspector General. Report No. 15n(39), USSBS Index Section 2
https://dl.ndl.go.jp/info:ndljp/pid/8815782
Douglas DC-2:
Manual for operating Model DC-2, Nakajima "Douglas" passenger plane, published by Nakajima Aircraft Corporation, October 1935.
http://dl.ndl.go.jp/info:ndljp/pid/8815744
Aircraft engine and other equipment manuals:
Manual with drawings for Type 100, 1,450 hp. Engine, October 1941.
https://dl.ndl.go.jp/info:ndljp/pid/8815755
Manual with charts for Type 98, 450 hp. Engine, July 1939.
https://dl.ndl.go.jp/info:ndljp/pid/8815756
Manual with drawings for Type 99, 900 hp. Engine (Models 1 and 2), May 1941.
https://dl.ndl.go.jp/info:ndljp/pid/8815757
Manual for Type "Hikari" (Model 1 and 2) engine, February 1936.
https://dl.ndl.go.jp/info:ndljp/pid/8815758
Manual for Type 2,1,150 hp. Engine, September 1944.
https://dl.ndl.go.jp/info:ndljp/pid/8815759
Elements of aircraft engines, September 1944.
https://dl.ndl.go.jp/info:ndljp/pid/8815761
Periodic maintenance of aircraft engines, October 1942.
https://dl.ndl.go.jp/info:ndljp/pid/8815762
Manual with drawings for Type 97, 650 hp. Engine, May 1938.
https://dl.ndl.go.jp/info:ndljp/pid/8815763
Manual with drawings for Type 97, 850 hp. Engine, May 1938.
https://dl.ndl.go.jp/info:ndljp/pid/8815764
Manual with drawings for Type 95, 800 hp. Engine, revised January 1938.
https://dl.ndl.go.jp/info:ndljp/pid/8815766
Manual with drawings for Type 95, 150 hp. Engine, December 1936.
https://dl.ndl.go.jp/info:ndljp/pid/8815767
Manual with drawings for Type 94, 550 hp. Engine (Model 2) November 1938.
https://dl.ndl.go.jp/info:ndljp/pid/8815768
Manual with drawings for Type "ju," 450 hp. Engine (Models 1 and 2) August 1945.
https://dl.ndl.go.jp/info:ndljp/pid/8815769
Manual for Kinsei engine, Model No. 51, prepared by Naval Air headquarters, December 1941.
https://dl.ndl.go.jp/info:ndljp/pid/8815770
Manual for Zuisei engine, Model No. 10, prepared by Naval Air headquarters, February 1941.
https://dl.ndl.go.jp/info:ndljp/pid/8815772
Data on Zuisei engine, Model No. 11, prepared by Naval Air headquarters, 1938.
https://dl.ndl.go.jp/info:ndljp/pid/8815773
Kotobuki engine, Model No. 2, modifications No. 1, No. 2, and No. 3, table of comparisons, November 1938-June 1940.
https://dl.ndl.go.jp/info:ndljp/pid/8815774
Manual for engine accessories, Part I, The Starter, prepared by the Naval Air headquarters. August 1942.
https://dl.ndl.go.jp/info:ndljp/pid/8815775
Manual for starter (induction and inertia) prepared by Naval Air headquarters, May 1936.
https://dl.ndl.go.jp/info:ndljp/pid/8815776
Airplane static eliminator manual prepared by Naval Air headquarters, June 1937.
https://dl.ndl.go.jp/info:ndljp/pid/8815777
Packing and loading of A / C parts for transporting purposes December 1940, by Ministry of Army.
https://dl.ndl.go.jp/info:ndljp/pid/8815779
Oxygen inspirator for Type 1 (Model 3), fighter, April 1945, Army Air Inspector General.
https://dl.ndl.go.jp/info:ndljp/pid/8815780
Oxygen inspirator for Type 3, fighter, March 1940, by Army Air Inspector General.
https://dl.ndl.go.jp/info:ndljp/pid/8815781
Oxygen inspirator for Type 4, heavy bomber, March 1940, by Army Air Inspector General.
https://dl.ndl.go.jp/info:ndljp/pid/8815782
Oxygen inspirator for Type 100, headquarters reconnaissance plane (Model 3 and 4), by Army Air Inspector General(two copies).
https://dl.ndl.go.jp/info:ndljp/pid/8815783
Experiments on electrical accessories for A / C, September 1942, Navy Air Technical Depot.
https://dl.ndl.go.jp/info:ndljp/pid/8815784
Rubber-insulated electric wire (double wire) December 1942, by Navy Air Technical Depot, branch depot.
https://dl.ndl.go.jp/info:ndljp/pid/8815786