Naokuni Nomura graduated from the 35th class of the Imperial Japanese Naval Academy on 20 November 1907, ranked 43rd out of 172 cadets. Also he graduated from the Naval Staff College with honors in 1920.
After commissioning to ensign on 25 December 1908, Naokuni Nomura was assigned to the destroyers Yayoi and Kamikaze. After completing naval artillery and basic torpedo training, he was assigned to the battleship Aki, and was promoted to sub-lieutenant on 1 December 1910.
Naokuni Nomura served successively as military attache to Japanese Embassy in Germany and captain of Haguro and Kaga; after being promoted to rank of rear admiral in 1934 became director of Navy Submarine School. As military attache to Japanese Embassy in China and staff member in Command of Japanese Fleet in China was stationed in Shanghai where he made futile efforts to bring about peace with the Chungking Government in 1988.
Upon arrival in Germany as chief Japanese Military Commissioner in 1940 iried vainly to persuade German authorities not to open war against Soviet Russia; following outbreak of World War II Naokuni Nomura worked for conclusion of military pact between Japan and Germany.