After his commissioning as a lieutenant junior grade, he completed naval artillery and torpedo school training and was assigned to the 3rd Submarine Squadron in December 1916.

He was dispatched to the Mediterranean with the Japanese fleet as part of Japan's contribution to the Anglo-Japanese Alliance in World War I and participated in combat operations as an officer on the destroyer Kashi based on Malta from July 1918.

In January 1919, he was assigned to a navigation unit with the naval squadron escorting Imperial German Navy submarines received by the Japanese government as part of reparation payments from Germany at the end of World War I.

In March 1921, Yamaguchi was sent to the United States to attend Princeton University at the Navy's expense, and returned to Japan in May 1923.

Assigned to the Japanese delegation at the London Naval Conference 1930, he joined Admiral Isoroku Yamamoto in vocal opposition to the terms of the disarmament treaty.

He served as an instructor at the Naval Staff College from November 1932 and was promoted to the rank of captain in December of that year.

Following the successful strike against the American fleet at Pearl Harbor, Yamaguchi′s carrier force participated in the Battle of Wake Island.

After the start of 1942, he was sent south to assist in the Battle of Ambon in the Dutch East Indies, followed by the Bombing of Darwin in February.

In March, his carriers supported Japanese forces in the Battle of Java, sweeping the Dutch East Indies of remaining Allied warships.

In April, he crossed into the Indian Ocean to support the large-scale raid against the Royal Navy at and near Ceylon.

Yamaguchi returned to Japan briefly in late April for maintenance on his fleet, at a time when the IJN General Staff was making plans for a Second Operational Phase of the Pacific War.

At that moment, the Japanese planes had been armed for a second strike on Midway, with the "Kate" level bombers carrying bombs rather than torpedoes.

Yamaguchi was posthumously promoted to the rank of vice admiral and awarded the Order of the Golden Kite, 1st class.

In the 1960 film Hawaii Midway Ocean Combat; The Storm in The Pacific (ハワイ・ミッドウェイ大海空戦 太平洋の嵐), Yamaguchi was portrayed by Toshiro Mifune.