Yamaguchi was in Hiroshima on a business trip for his shipbuilding company on Aug. 6, 1945, when a U.S. B-29 dropped an atomic bomb on the city. He suffered serious burns to his upper body and spent the night in the city.
He then returned to his hometown of Nagasaki, about 300 kilometers (190 miles) southwest, which suffered a second U.S. atomic bomb attack three days later.
On Aug. 15, 1945, Japan surrendered, ending the war.
The mayor of Nagasaki said “a precious storyteller has been lost,” in a message posted on the city’s Web site Wednesday. Yamaguchi died Monday morning of stomach cancer, the mass circulation Mainichi, Asahi and Yomiuri newspapers reported.