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 flights, the ship trained naval pilots. Shortly after Kasuga Maru arrived at Rabaul on 11 April, the harbor was bombed twice, although the ship was not harmed in the attacks. On 14 July, she was assigned to the Combined Fleet, along with her sister, .