As captain of the Amatsukaze Commander Hara participated in the Battle of the Java Sea, the capturing of the hospital ship SS Op Ten Noort and the sinking of the submarines HNLMS K X and USS Perch, and the occupation of Christmas Island.

[2] He wrote in his memoirs of having spotted Perch in the darkness of the night after detecting it when he saw a sailor topside on the vessel light a cigarette an estimated 4,000 meters (4,400 yd) away.

[4] After Amatsukaze returned to Japan for repairs, Hara was promoted to captain and given the command of Destroyer Division 27, flying his flag aboard Shigure.

While on a re-supply mission through Blackett Strait on 2 August 1943, Hara noticed a fireball exploding near leading destroyer Amagiri and ordered Shigure's crew to shoot at the burning wreckage of Lt. John F. Kennedy's patrol torpedo boat PT-109.

[5] During the Battle of Vella Gulf on 6–7 August Shigure was the only one of four Japanese destroyers to escape, though she was later found to have been hit by a torpedo, passing through the rudder, that failed to explode.

[8] Hara's last sortie was as captain of the light cruiser Yahagi as flagship of the destroyer screen accompanying Yamato on her fateful last mission as part of Operation Ten-Go.

Hara ended the war at Kawatana training Japanese sailors to operate Shinyo suicide boats, where he witnessed firsthand the effects of the second atomic bombing.