Kawasaki laid down Submarine No. 403 at Senshu, Japan, on 20 June 1942. Renamed Ro-112 the following February, she was launched on 25 March 1943 and commissioned that September. The Ro-100 class was derived from the preceding Kaichu type -- medium-sized boats designed for coastal and defensive operations rather than the long-range commerce raiding that larger fleet submarines conducted. At 60.9 meters long with a beam of just 6 meters, she was compact by submarine standards. Two 500-horsepower diesel engines drove her at 14.2 knots on the surface; submerged, a pair of 380-horsepower electric motors managed 8 knots. Her armament was modest: four bow torpedo tubes carrying eight torpedoes total, supplemented by 25mm anti-aircraft guns. Her surface range of 3,500 nautical miles at 12 knots was enough for operations across the western Pacific, but she was no ocean-crosser. She was built to patrol, intercept, and survive -- and for nearly two years, she did exactly that.

Ro-112's most harrowing assignment came in May 1944, when she joined Scouting Line NA, a submarine picket line north of the Admiralty Islands tasked with detecting any Allied move toward the Palau Islands. It was a dangerous posting. On 18 May, U.S. Navy signals intelligence intercepted and decrypted the Japanese communications that established the line. A hunter-killer group of destroyer escorts sortied from Purvis Bay in the Solomon Islands and systematically attacked the submarines on station, sinking several. The Japanese 6th Fleet, in a grim irony, then intercepted and decrypted an American message reporting the destruction. The warning reached Ro-112 in time. Her commanding officer moved the boat 100 nautical miles northwest of her assigned patrol area -- far enough to avoid the hunters. She slipped away and reached Truk on 8 June 1944. Two subsequent patrols in the Philippine Sea passed without incident, a kind of quiet that in submarine warfare counts as success.

By autumn 1944, the war's trajectory was unmistakable. In August, Submarine Division 51 was disbanded, and Ro-112 was reassigned to the Kure Submarine Squadron as a training vessel. The reprieve was temporary. When Operation Sho-Go 1 activated on 13 October in anticipation of the American invasion of the Philippines, Ro-112 was pulled back into combat, reassigned to Submarine Division 34 under Combined Fleet headquarters. Her sixth and seventh patrols -- into the Philippine Sea and Lamon Bay off Luzon -- were uneventful. She returned to Kure on 28 December 1944. Three weeks later, she departed on what would become her final mission: a patrol in the South China Sea west of Luzon. But the original orders were soon superseded. On 4 February 1945, the 6th Fleet directed Ro-112 to proceed to Takao in Formosa, offload her reserve torpedoes and deck gun ammunition, then head for Batulinao on Luzon's northern coast to evacuate stranded Japanese pilots. The submarine had become a transport.

On the evening of 11 February 1945, Ro-112 was running on the surface in the Luzon Strait near Camiguin Island when the American submarine USS Batfish detected her radar emissions. Batfish picked up the contact at 18:51 at a range of 8,000 yards. She closed, sighting Ro-112 visually at 1,300 yards before the Japanese boat submerged at 20:43. Fourteen minutes later, Batfish's sonar operator heard ballast tanks blowing. Ro-112 surfaced at 21:06, her radar sweeping again. Batfish reacquired the contact at 8,650 yards, closed to 6,000 yards, and submerged to radar depth. At 22:02, Batfish fired four Mark 18 torpedoes from her bow tubes at a range of 880 yards. The first torpedo struck Ro-112 and blew her apart. She sank immediately with the loss of all 61 crew members. Nine days later, the Imperial Japanese Navy declared her presumed lost. She was struck from the Navy list on 10 May 1945, three months before the war's end. Sixty-one men who had survived seven patrols did not survive the eighth.