Private First Class Yoshihara was a member of Headquarters and Headquarters Company, 27th Infantry Regiment, 25th Infantry Division. He was wounded by the enemy in South Korea on 28 July 1950 and returned to duty later that day. He was Killed in Action while fighting the enemy in South Korea on 25 August 1950. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Private First Class Yoshihara was awarded the Silver Star Medal, the Purple Heart with Oak Leaf Cluster, the Combat Infantryman Badge, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.