CINCPAC item 9718 Research on Striking Force Tactics: Yokosuka Naval Air Group Reference 45 20 May 1943. This is the so called "Japanese Carrier Manual" referred to in a number of histories. It is the document that Admiral Spruance had seen before the Marianas. 2 parts http://dreadnoughtproject.org/friends/dickson/Strike%20Force%20Tactics%201-18.pdf
http://dreadnoughtproject.org/friends/dickson/Strike%20Force%20Tactics%2019-32.pdf
JICPOA Item 5782 Battle Lessons Learned in the Greater East Asia War (Torpedoes), Volume VI. This Volume of Batte Lessons has as its subject the night battle fough from April to September 1943 and is based on detailed battle reports from the Expeditionary Investigation Committee. 1 part. http://dreadnoughtproject.org/friends/dickson/JapaneseBattleLessonsTorpedoes_1944.pdf
JICPOA Item 5782A Battle Lessons Learned in the Greater East Asia War (Torpedoes), Volume VI Annexed Volume 1 Motor Torpedo Boats (Gyoraitei-PT Boats). These battle lessons are comprised of lessons relating to PT boats from the beginning of the Greater East Asia War to September 1943. 3 parts
http://dreadnoughtproject.org/friends/dickson/MTB%20IJN%201.pdf
http://dreadnoughtproject.org/friends/dickson/MTB%20IJN%202.pdf
http://dreadnoughtproject.org/friends/dickson/MTB%20IJN%203.pdf
Japanese Aerial Tactics against Ship Targets JICPOA WEEKLY INTELLIGENCE BULLETIN 20 October 1944 From sources such as captured Japanese pilots notebooks, 11 Recon Squadron Standing Orders, Southeast Area Fleet ir Combat Doctrine and other captured Japanese documents. 3 parts http://dreadnoughtproject.org/friends/dickson/Japanese%20Aerial%20Tactics%201.pdf
http://dreadnoughtproject.org/friends/dickson/Japanese%20Aerial%20Tactics%202.pdf
http://dreadnoughtproject.org/friends/dickson/Japanese%20Aerial%20Tactics%20correction%20pages.pdf
ATIS Research Report 96 15 June 1945: Signal Flags used by Japanese Naval and Merchant Ships. This report sets forth information available to ATIS files up to January 1945 pertaining to signal flags used by Japanese naval and merchant vessels which appear to be unusual, or to irregular combinations of flags with other emblems.
In my research I have uncovered a good deal about IJN signaling and as a result compiled this home made signal book.It is based on original materials but is not the Japanese Navy's Signal Book: http://david.ijn.googlepages.com/completesignalbook
The Imperial Japanese Navy in World War II. A graphic Presentation of the Japanese Naval Organization and a List of Combatant and Non=Combatant Vessels Lost or Damaged in the War. Prepared by Military History Secton, Special Staff, General Headquarters,Far East Command, February 1952
http://ww2db.com/other.php?other_id=15
The following handbooks were prepared by me in the 1970s based on original sources and are added though they are not original themselves. http://pages.google.com/edit/david.ijn/ijncruiserandbattleshipdoctrine?authtoken=8e834456a0bae11eee8b06f585638725d52b17b0
Japanese Mission to Italy, 1941: This is an article that appeared in the January 1956 U. S. Naval Institute Proceedings. Written by Vice Admiral Giuseppe Fiorvanzo, Italian Navy it recounts the Japanese Mission to Italy in the spring of 1941. It is of interest for two reasons. First it spells out Japanese carrier tactics at that time (just before the formation of First Air Fleet) and second it clearly spells out their views on night fighting, particularly the big night battle described in much more detail in Kaigun.
http://dreadnoughtproject.org/friends/dickson/Japanese%20Mission%20to%20Italy%201941.pdf