In between transport missions, the ship trained naval aviators. Shortly after Kasuga Maru arrived at Rabaul on 11 April, the harbor was bombed twice, although the ship was not damaged in the attacks. On 14 July, she was assigned to the Combined Fleet, together with her sister, .
Between missions, the ship trained naval pilots. Following Kasuga Maru's arrival at Rabaul on 11 April, the harbor was bombed twice, but the ship avoided damage in the attack. On 14 July, she was assigned to the Combined Fleet, along with her sister, .