On 13 May 1943, "I-36" was assigned to the Northern Unit in the 5th Fleet for service in the Aleutian Islands campaign. Before departing Japan for the Aleutian Islands, she took part in towing tests for the "Unkato" cargo container — a submersible cargo container that could carry up to 377 tons of supplies, designed for a one-way trip in which the cargo′s recipients released, recovered, and unloaded it — in the Seto Inland Sea on and again from 3 to 5 June 1943. She then departed Kure at 10:00 on 7 June 1943 bound for Paramushiro in the Kurile Islands, which she reached on 13 June 1943.