[1] For surface running, the boats were powered by two 500-brake-horsepower (373 kW) diesel engines, each driving one propeller shaft.

[4] After calling at Wewak on 27 May 1944 and unloading her cargo, she got back underway the same day and proceeded to Palau, where she arrived on 3 June 1944 to deliver secret Imperial Japanese Army documents including codebooks.

[4] She was 550 nautical miles (1,020 km; 630 mi) northwest of Rota on 19 June 1944 when she sighted two groups of United States Navy aircraft carriers and their escorts, and at 18:07 Japan Standard Time she fired four torpedoes at what her commanding officer described as a "Saratoga-class" aircraft carrier, but they all missed.

[4] The escorts subjected her to a brief counterattack with depth charges, but she escaped unscathed and received orders to return to Truk, where she arrived on 27 June 1944.

[4] On 10 August 1944, she departed Yokosuka bound for Penang in Japanese-occupied British Malaya, from which she was to conduct operations in the Indian Ocean.

[4] Based on traffic analysis of Japanese signals, Fleet Radio Unit, Melbourne (FRUMEL), an Allied signals intelligence unit headquartered at Melbourne, Australia, reported that an Allied aircraft had attacked Ro-115 on 28 October 1944 at 15°28′N 090°15′E / 15.467°N 90.250°E / 15.467; 90.250 and might have sunk her,[4] but FRUMEL revised its analysis and reported correctly on 6 November 1944 that Ro-115 remained active.

[4] At 19:55 on 31 January 1945, the U.S. Navy light cruiser USS Boise (CL-47) was off Mindoro 125 nautical miles (232 km; 144 mi) southwest of Manila when she detected a surface contact on radar.

[4] Bell and the destroyer USS O'Bannon (DD-450) closed to investigate, and the target disappeared from radar, indicating a submerging submarine.

[4] As the destroyer escort USS Ulvert M. Moore (DE-442) headed for the scene to join the hunt, Bell regained sonar contact on the submarine and made another depth-charge attack, which resulted in an oil slick appearing on the surface.

[4] Ro-115 never acknowledged any of the orders, and FRUMEL reported on 16 February 1945 that Japanese messages indicated that Ro-115 still had not arrived at Takao to unload her ammunition and torpedoes.

[4] On 21 February 1945, however, the Imperial Japanese Navy declared her to be presumed lost off the Philippine Islands with all 59 men on board.