Departing on her second war patrol 21 July 1944, "Guitarro" set course for the South China Sea off the west coast of Luzon. She commenced her approach to the lead escorts of a large convoy 7 August and after missing the first target scored three hits on frigate "Kusakaki", blowing off her bow and sinking her in a spectacular explosion. The remainder of the convoy escaped as "Guitarro" eluded the determined attacks of an escort destroyer. She surfaced the next day to sink a small coastal vessel with her deck gun, and then steamed toward Cape Bolinao, where she was to rendezvous with the next day.