29-year-old Yamaguchi was in Hiroshima on a business trip for the firm at which he worked as an engineer. That morning, he set out to the city's shipyard to say farewell to his colleagues at Mitsubishi Heavy Industries before heading home from the three-month trip. On his way to the train station to head back to his home in Nagasaki, he noticed he’d forgotten his travel permit and went back to get it.
He picked up his pass and was on his way back to the station when he saw a bomber flying over the city and “two small parachutes”, then a rush of blinding light, sound, wind, and heat knocked him to the ground. Being about 3 km from the nuclear blast, he was severely burned, temporarily blinded, and rendered permanently deaf in his left ear.
"I didn't know what had happened. I think I fainted for a while. When I opened my eyes, everything was dark, and I couldn't see much. It was like the start of a film at the cinema, before the picture has begun when the blank frames are just flashing up without any sound," he later told the British paper The Times.
Yamaguchi spent the night in an air raid shelter before returning home to Nagasaki, 180 miles away. He limped to the hospital upon arrival. The doctor who treated him was a former school classmate, but the blackened burns on Yamaguchi’s hands and face were so severe that the man didn’t recognize him at first. Neither did his family. When he returned home afterwards, feverish and swaddled in bandages, his mother accused him of being a ghost.
Bandaged up and suffering from his exposure to radiation, Yamaguchi was nonetheless back at work on 9 August, telling his sceptical boss exactly what had happened in Hiroshima and describing the scale of the devastation, a city swallowed whole by one single bomb.
As he was talking, and his supervisor was calling him "crazy", a white light burst through the window and filled the room. American pilots of the Bockscar B-29 bomber had just unloaded another atomic bomb on Nagasaki. Yamaguchi was hit again.
The combined death toll of the Hiroshima and Nagasaki atomic bombings is thought to be as high as 250,000. The combined payload of the two bombs – Little Boy in Hiroshima and Fat Man in Nagasaki – was equivalent to 36,000 tonnes of TNT.
Somehow, despite their house being destroyed, his wife and son also survived the blast. They spent the week in an air raid shelter.
In the days the followed, Yamaguchi’s double-dose of radiation took its toll. His hair fell out, the wounds on his arms turned gangrenous, and he began vomiting incessantly. However, he slowly recovered and went on to live a relatively normal life. He served as a translator for the U.S. armed forces during their occupation of Japan, and later taught school before resuming his engineering career at Mitsubishi. He and his wife even had two more children in the 1950s, both of them girls.
It was only in 2005 that Yamaguchi began speaking publicly about having survived both blasts. In 2009, the Japanese government officially recognized his claim by verifying it, though there are supposedly more than 150 others like him.
The bomb that hit Nagasaki was even more powerful than the one dropped on Hiroshima, but as Yamaguchi would later learn, the city’s hilly landscape and a reinforced stairwell had combined to muffle the blast inside the office. His bandages were blown off, and he was hit by yet another surge of cancer-causing radiation, but he emerged relatively unhurt.
"My double radiation exposure is now an official government record," Yamaguchi told reporters at the time. "It can tell the younger generation the horrifying history of the atomic bombings even after I die."
Yamaguchi died of stomach cancer at a hospital in Nagasaki in 2010. His wife lived to 88, dying of kidney and liver cancer. Their son died aged 59.
In the last year of his life, Yamaguchi said: "My double radiation exposure is now an official government record. It can tell the younger generation the horrifying history of the atomic bombings even after I die. I could have died on either of those two days. Everything that follows is a bonus."
