Captain Hiroshi Imazato was born in Nagasaki on September 24, 1896. He graduated from the Etajima Naval College in November 1917, and then took went to the Torpedo School in Yokosuka Naval Station , and later specialized in submarines, becoming commander of the 20th Submarine Division in November 1939.

On August 11, 1941, he became commander of the 1st Submarine Division and switched to the 2nd Submarine Division in February 1942. He eventually became commander of Hokoku Maru on August 25, 1942. He was promoted to Rear-Admiral posthumously.