 Upon the submarine's return to Kure, Hashimoto was detached and assigned to the advanced course at Submarine School on 1 February 1942, to prepare him for command of a submarine. Graduating from this course on 30 June, Hashimoto was given command of submarine Ro-31, a coastal defense vessel. For the remainder of 1942, Hashimoto operated his ship in home waters off Yokosuka training crews and trying new equipment and doing research for the development of Japanese submarine doctrine. He was promoted to lieutenant commander on 1 November. In 1943, he was given command of submarine I-158 for coastal defense, and later in the year was given command of submarine Ro-44 for the same duties.
