Hira was a river gunboat, named for the Hira mountains, and one of the four Seta-class boats. Her sisters were Seta, Katata, and Hozu. Mitsubishi at Kobe laid her down on 15 August 1921. The launch is three dates. The officer list says 14 March 1922. The usual ship account says 14 March 1923. The movement record says 24 March 1923. She was completed on 24 August 1923, taken apart, and shipped to Hankow. Yangtze Engineering put her back together there. One account has her moving on the river in September. Another finishes the reassembly on 1 December. She spent her life on the Yangtze. For a time she was the boat based at Chongqing.
On 13 December 1937 the 11th Gunboat Sentai went up to Xiaguan as Japanese troops entered Nanjing. Hozu and Seta were in front. Hira came with the boats behind them. They fired on the trenches and on the boats and rafts along the bank. The names before 1939 disagree from list to list, and those tours are left out. Toshi Kubota had her from 25 September 1939 to 15 October 1940. From that day until 20 August 1941 the lists do not agree on the captain. One says Takeyoshi Dobashi. The other says Toshimi Tsuchihashi. He is not filed. Tsuneo Sakamoto, who had just left Mikazuki, took her on 20 August 1941.
On 31 May 1943, upriver from Hankow, American fighters hit the engine room, the boiler room, and the bridge. She could not move. Eight men were killed. Sakamoto was one of them. Tadaomi Murakami had her from 4 June 1943. The officer list ends that tour in April 1944 and does not give the day. The last name in that list, Yoshio Kawata, has only a month for his start, so he is not filed. The list runs his tour to 26 November 1944.
On 17 August 1944 American aircraft damaged her at Kiukiang. On 26 November 1944 she and Hozu ran aground in shallow water near Anking. The movement record says Chinese aircraft badly damaged her and sank Hozu, at about 30°30′N, 117°00′E. The officer list calls Hira sunk that same day, at that same position. She was taken apart for scrap in the spring of 1945 and struck on 10 May 1945. One ship table puts the discard on 30 September 1945. No gun count is given here. The lists do not agree on a fit that can be checked against this hull.