With 14–15 hours of daylight, she hunted in the coastal and inter-island shipping lanes to Muroran, Matsuwa, and Paramushiro. On 24 August, she attacked and sank "Tosei Maru" off Erimo Saki. On 5 September, after a six-hour chase, she fired four torpedoes at a maru with one escort. All of her torpedoes missed. On the night of 8 September, she encountered a two-column, six-ship convoy with an escort on each wing, and closed in to the leading ship. Shortly after 2045, she fired four torpedoes at overlapping targets, then opened to the eastward as the torpedoes started hitting. Just before midnight, she again attacked the convoy, now comprising only four ships. One freighter took two hits. A second maru turned to chase "Seal". "Seal" retired briefly, and just before 0300 on 9 September, hit the remainder of the convoy. Daylight brought antisubmarine aircraft to the scene, and "Seal" fishtailed at deep submergence until 1700. At 2026, having sunk "Shonan Maru" and damaged three or four other ships, she headed for Midway, arriving on 17 September.