Refit completed and her crew rested, "Tench" (now skippered by Tom Baskett) returned to sea early in May for her second war patrol. That patrol took her again to the Japanese homeland, but this time to the Tsugaru Strait between Honshū and Hokkaidō, the northern entrance to the Sea of Japan. Her mission was to interdict Japanese shipping as it attempted to run north and south between the Kuril Islands and Tokyo. Her first contact came on 25 May and proved to be an enemy warship. While patrolling on the surface, she sighted a periscope approaching her out of the fog. She submerged immediately, picked the enemy up on her sound gear, and evaded him successfully. During the waning days of May, she sighted little enemy shipping of consequence though her gun crews dispatched a number of motor luggers, picket boats, steam trawlers, and other small craft to the depths.