On 20 April 1945, "I-121" and "I-122" were resubordinated to Submarine Division 33 in the Kure Submarine Squadron. "I-121" was transferred to the Maizuru Naval Base on 12 June 1945 and remained there through the end of World War II. Hostilities ceased on 15 August 1945, and Japan formally surrendered on 2 September 1945. "I-121" surrendered to the Allies in September 1945 at Maizuru.