The Kōtoku Maru was a 6,702 gross ton freighter that was built by Mitsubishi Jūkōgyō Kabushiki-kaisha, Nagasaki for Hiroumi Syozi Kabushiki Kaisha launched in 1937.
Disembarkation of her embarked troops of the 15th Independent Engineer Regiment began near the village of Basabua on the afternoon of 29 July 1942.
The ships of the convoy came under bombardment from eight United States Army Air Forces (USAAF) A-24 Banshees of the 3rd Bombardment Group from 7-Mile Drome near Port Moresby, New Guinea, escorted by USAAF P-39 Airacobras of the 41st Fighter Squadron and 80th Fighter Squadron at 1445.
After heading back under her own power to Lae, she was quickly patched up to return the following day to offload the much-needed equipment.
On 30 July, under the protection of the light cruiser Tatsuta and destroyer Yūzuki, she headed back to Buna at 1330.