On 29 December, she left on her first war patrol, steaming for the Mariana Islands. She arrived off the coast of Guam at 03:00 on 11 January 1945 and Hashimoto ordered four "kaitens" launched. The kaitens tentatively claimed a tanker sunk, though it was unable to verify if the ship had actually been struck. The strike had been unsuccessful. She then sped back to Kure and arrived there on 20 January. She remained in port there until March, likely due to supply shortages. On 1 March, she was ordered to Iwo Jima to support the battle taking place there. Once there, "I-58" was ordered to launch all of its "kaitens" without their pilots and immediately return home. She was ordered out again on 2 April sailing to support Japanese forces at the Battle of Okinawa. While there, she was attacked by aircraft 50 times. She never surfaced for more than a few hours. She limped to Kure on 29 April 1945, the only Japanese submarine to withdraw from the operation. She remained in port because of continued mining conducted by U.S. Army Air Forces, and departed on 16 July on another war patrol. At the time, she was one of only four large submarines left in the Japanese Navy, and her mission was to harass Allied lines of communications.