Who is the only person to be officially recognised as surviving both the Hiroshima and Nagasaki atomic bombings?

Tsutomu Yamaguchi

"At around 8:15am on the morning of August 6, 1945, Tsutomu Yamaguchi was heading to his place of work when he looked up and noticed a B-29 bomber soaring over Hiroshima. A small object attached to two parachutes dropped out of the plane and the next thing Yamaguchi remembered was a flash of light like a magnesium flare hurtling towards the city.

The 13-kiloton uranium atomic bomb, known as Little Boy, destroyed much of Hiroshima. Just three kilometers from the epicenter of the blast, Yamaguchi was violently pushed back before instinctively taking cover in an irrigation ditch. A nautical engineer, he'd been sent to Hiroshima three months earlier by his boss at Mitsubishi Heavy Industries to work on an oil tanker. It was supposed to be his penultimate day in the city and he was desperate to get back to his family.

Suffering from a ruptured eardrum and badly burned on the upper part of his body, the then 29-year-old spent an anxious night at an air raid-shelter with colleagues. Passing through scenes of anguish and torment, he then headed toward to the west of the city the following day to get to the station.

With the bridges down, he had to cross a river that was full of bloated corpses of men, women and children, some of whom were stuck together. These disturbing images would remain with Yamaguchi until his death, yet at the time his main concern was simply reaching the other side. Wading through the dead bodies, he eventually made it across.

Remarkably, the train was still running. Yamaguchi returned to his hometown of Nagasaki on August 8. He went to the hospital to get his burns treated and within 24 hours was back at work. While in the middle of explaining to a disbelieving boss what he'd witnessed in Hiroshima the engineer was thrown back again by yet another explosion."

https://www.tokyoweekender.com/2020/08/tsutomu-yamaguchi-man-who-survived-atomic-bombs/

The Wikipedia article for Tsutomu Yamaguchi actually says that at least 70 people are known to have survived both atomic bombings, however the Japanese Govt has only ever officially recognised Yamaguchi as surviving both explosions.

Tsutomu Yamaguchi (?? ?, Yamaguchi Tsutomu) (March 16, 1916 - January 4, 2010) was a Japanese marine engineer and a survivor of both the Hiroshima and Nagasaki atomic bombings during World War II. Although at least 70 people are known to have been affected by both bombings,[1] he is the only person to have been officially recognized by the government of Japan as surviving both explosions.[2]

https://en.wikipedia.org/wiki/Tsutomu_Yamaguchi

Unfortunately, the link [1] to the source of the claim of "at least 70 people..." is a Japanese article written in Japanese, but we can safely assume it has been verified.

I believe the distinction is having "been affected" and "survived both explosions", and I'm sure there were probably more than 70 people that were affected by both, the key is documentation, and only 70 were documented. You wouldn't necessarily have to be present during the explosion to have been affected by both, they are only about 260 miles(421km) apart. back in 1994 I toured Nagasaki and there was a hospital specifically dedicated to the treatment and long term study of the atomic bomb survivors.

Going back to the original source, the director of the movie about Yamaguchi names at least two other people who survived both, as discussed in the flooring excerpt:

In 2009, less than a year before his death, the Nagasaki native became the only person to be officially recognized by the government of Japan as a double hibakusha (survivor of atomic bomb). As filmmaker Hidetaka Inazuka points out, though, there were many others, including Yamaguchi's colleagues Akira Iwanaga and Kuniyoshi Sato.

"Mitsubishi had factories in Hiroshima and Nagasaki so numerous workers would have boarded the same train as Yamaguchi-san," says Inazuka, who directed the 2011 documentary Twice Bombed: The Legacy of Tsutomu Yamaguchi (also on Netflix). "The majority of them would have perished in the second attack, however, while it's difficult to confirm exact figures, we know there were over one hundred survivors."