He stayed with Soya on its cruise the following year to Manila, Ambon, Townsville, Brisbane, Sydney, Hobart, Melbourne, Fremantle, Batavia, Singapore, Hong Kong, Makung, and Keelung.

Shortly after his promotion to ensign on December 15, 1910, he was reassigned to the cruiser Kurama and attended the coronation ceremonies for King George V in London in 1911.

In 1912, he returned to school to study latest naval artillery and submarine warfare techniques and was promoted to sub-lieutenant at the end of that year.

Although Fusō participated in operations in World War I against the Imperial German Navy, Inoue was not in any combat situations.

At the end of 1918, Inoue was appointed military attaché to Switzerland, and ordered by the Navy to learn German.

Inoue remained in staff positions for the next several years, including an appointment as naval attaché to Italy from 1927 to 1929, after which he was promoted to captain.

Inoue was a protégé of Admiral Isoroku Yamamoto, and was strongly opposed to the Tripartite Pact with Fascist Italy and Nazi Germany.

Inoue was a leader of the "leftist clique" within the Japanese military, which opposed Japan's increasing trend towards fascism and overseas expansionism.