Afterwards, as a lieutenant commander, he was sent to Stanford University in California from 1933 for further studies, but his real role was to work in naval intelligence to build a spy ring and gather information on American military activities on the west coast of the United States.

Tanni”, he recruited former Navy yeoman Harry Thomas Thompson, in San Pedro, California in the run-up to World War II.

Through this and other methods, he was able to sell engineering, gunnery, and tactical information about the Pacific Fleet that was mainly based in nearby San Diego at that time.

The incident was highly publicized, including in a 1943 novel by Alan Hynd, Betrayal from the East: The Inside Story of Japanese Spies in America which was subsequently made into a movie.

He subsequently was promoted to captain and served as commander of Destroyer Division 17 in the Southwest Pacific from 17 June to 18 December 1943, followed by a posting as senior instructor at the Torpedo School in Oppama.