Maizuru Naval District
Upon commissioning, "Ro-45" was attached to the Maizuru Naval District and assigned to Submarine Squadron 11 for workups. On 14 April 1944, she was reassigned to Submarine Division 34 in the 6th Fleet. She departed Kure, Japan, on 16 April 1944 bound for Truk, which she reached on 27 April 1944.