"No. 1" was laid down at Kure Naval Arsenal on 5 November 1943 and launched on 8 February 1944. On 10 May, "No. 1", with Lieutenant Commander Shinbori Masao in command, was completed and assigned to the Yokosuka Guard Force. On 29 May, "No. 1" departed from Tokyo with the torpedo boat and three submarine chasers to escort convoy No. 3530 to Saipan, consisting of nine transports carrying troops of the Imperial Japanese Army's 43rd Infantry Division as well as regular supplies. During the journey, "No. 1" served as an anti-submarine vessel, conducting sweeps between 1 June to 6 June, but these did not deter American submarines, which sank five transports of the convoy in that time period. On 11 June, the convoy finally arrived at Saipan, but was forced to flee due to the invasion of the island by the United States Marine Corps.