 Hiyoshi Maru left Kupang on 16 January and was given air cover for the outward leg by an Aichi D3A2 "Val" dive bomber which reportedly attacked an Allied submarine en route. On 17 January, Hiyoshi Maru visited the Ashmore Reef area. The following day the crew landed on the tiny and uninhabited Browse Island, about 100 mi (87 nmi; 160 km) north west of the mainland. On the morning of 19 January, Hiyoshi Maru entered York Sound on the mainland. Although the crew saw smoke emanating from hills to the east of their location, they nevertheless anchored and camouflaged the vessel with tree branches. Local historians state that Matsu Kikan landing parties went ashore near the mouth of the Roe River (15°08 ′ 16 ″ S 125°23 ′ 11 ″ E). They reportedly explored onshore for about two hours, and some members of the mission filmed the area using an 8 mm camera. The Matsu Kikan personnel spent the night on the boat and reconnoitred the area again the following day, before returning to Kupang. The Japanese did not sight any people or signs of recent human activity and little of military significance was learnt from the mission.
