Kammala jumla mai zuwa: A ranar 20 ga Afrilu, 1945, "I-121" da "I-122" an sake sanya su zuwa Rukunin Jirgin Ruwa na 33 a cikin Kure Submarine Squadron. "I-121" an canza shi zuwa Maizuru Naval Base a ranar 12 ga Yuni 1945 kuma ya kasance a can har zuwa ƙarshen Yaƙin Duniya na II. An dakatar da tashin hankali a ranar 15 ga Agusta, 1945, kuma
Japan ta mika wuya a ranar 2 ga Satumba, 1945. "I-121" ya mika wuya ga Allies a watan Satumbar 1945 a Maizuru.