The Ro-100 class was a medium-sized submarine derived from the earlier Kaichu type, designed for coastal and regional operations rather than the long-range patrols of Japan's larger fleet boats. Ro-110 displaced 601 long tons on the surface and 782 submerged. Her double hull allowed a diving depth of 75 meters. Two 500-horsepower diesel engines drove her at 14.2 knots on the surface; submerged, a pair of 380-horsepower electric motors pushed her at 8 knots. Her range was 3,500 nautical miles at 12 knots on the surface, shrinking to just 60 nautical miles at 3 knots underwater. She carried eight torpedoes for her four bow tubes, along with anti-aircraft armament. These were not the legendary boats of the Pacific war but workmanlike submarines sent to disrupt Allied shipping lanes in the Indian Ocean, where convoys moved supplies between India, Ceylon, and the ports of Southeast Asia.

During one of her patrols, a submarine torpedoed the British armed merchant ship Daisy Moller just 3 nautical miles off India's coast near the Eastern Ghats. The 4,807-gross-register-ton vessel had departed Bombay on 27 November 1943 carrying war materials including ammunition, stopped briefly at Colombo in Ceylon, and departed on 8 December steaming independently toward Chittagong. After the torpedo struck and the crew abandoned ship in three lifeboats and several life rafts, what followed went beyond warfare. The submarine surfaced and rammed the lifeboats, smashing them and spilling their occupants into the sea. The crew then machine-gunned the survivors in the water. Sources disagree on the exact casualty figures, but some accounts record that of a crew as large as 127, only 14 survived. These were not soldiers in combat but merchant sailors in the water, defenseless, and the attack on them was a war crime by any standard.

Ro-110's final action came against Convoy JC-36, bound from Colombo to Calcutta through the Bay of Bengal. She fired two torpedoes into the British merchant ship Asphalion, a 6,274-gross-register-ton vessel. The hits killed six crew members and injured ten more, flooding the number 3 hold and the engine room and crippling the ship. Asphalion's surviving crew abandoned her, though she remained afloat and was eventually towed to port. But the convoy's escorts were already hunting. A Royal Indian Navy sloop and Royal Australian Navy corvettes gained sonar contact on Ro-110 and attacked with depth charges. The crews observed a large amount of oil rising to the surface and heard several heavy underwater explosions. On 15 March 1944, the Imperial Japanese Navy declared Ro-110 presumed lost with all 47 hands. She was struck from the Navy list on 30 April 1944.

The Bay of Bengal is not usually remembered as a major theater of submarine warfare, overshadowed by the Atlantic and Pacific campaigns. But for the merchant sailors who carried supplies between India, Ceylon, and the front lines in Burma, these waters were deadly. Japanese submarines operated across the Indian Ocean, targeting the convoys that sustained the Allied war effort in Southeast Asia. Ro-110's story captures the full spectrum of that campaign: the industrial efficiency of submarine construction at Kobe, the isolation of merchant vessels steaming alone through hostile waters, the horror of survivors attacked in the sea, and the swift retribution that Allied escort forces could deliver when they found their target. The 47 Japanese submariners who died aboard Ro-110 were young men sent to wage war in a distant ocean. The sailors they killed and terrorized were workers carrying cargo to keep armies supplied. Beneath the Bay of Bengal, their fates converged.