In his only interview with a British newspaper, he tells David McNeill about the moment when the same white light filled the room again.
Tsutomu Yamaguchi must be one of the luckiest people on the planet. He was in his twenties when he found himself in Hiroshima on the morning of Aug 6 1945, as a single B-29 US bomber droned overhead. That "Little Boy" bomb killed or injured 160,000 people by the day's end.
Despite being 3km (just under two miles) from Ground Zero, the blast temporarily blinded him, destroyed his left eardrum and inflicted horrific burns over much of the top half of his body.
Later, Tsutomu Yamaguchi headed to his home Nagasaki. 2 days later on Aug 8 1945, the "Fat Man" bomb was dropped, killing 70,000 people and creating a city where, in the words of its mayor, "not even the sound of insects could be heard".
In a bitter twist of fate, Yamaguchi was again 3km from the centre of the second explosion. In fact, he was in the office explaining to his boss how he had almost been killed days before when suddenly the same white light filled the room.