Oigawa Maru was a transport of the Imperial Japanese Navy, typed as an AP. In early March 1943 she was a transport in the Bismarck Sea convoy.
That convoy was caught in the Battle of the Bismarck Sea. The battle is dated 2 March 1943, and the result recorded for Oigawa Maru is that she was sunk.
Her fate is sinking by Allied aircraft on 2–3 March 1943, still within the Battle of the Bismarck Sea. The loss is laid to air attack.
A strike dated 3 March 1943 records bombs dropped on Oigawa Maru by an attacker who is left unknown. Those bombs sank her.
Credit for the sinking rests with Allied aircraft as a whole. The account assigns the loss to no single plane. Sunk in that battle, the transport’s hull was gone.