Yaguchi was born on November 14, 1932, in Kure, a suburb of Hiroshima, Japan, on November 14, 1932 into a farming family. The youngest of five children, he had a carefree youth but was aware of the clouds of war. World War II impacted his life, at the end of the war, when he was assigned a job at a shipyard. On the morning of August 6, 1945, while he was waiting to enter the factory building at the shipyard, he saw the flash of the atomic bombing of Hiroshima.