On Dr. Masakazu Fuiji In John Hersey's 'Hiroshima'

In the book Hiroshima by John Hersey, six characters were shown as survivors during the Hiroshima bomb in 1945. The highlighted character given was Dr. Masakazu Fuiji. Out of the six characters that were chosen by Hersey, Dr. Fuiji was one of two scientists, but may have been the most affected or hurt out of the characters. He was never constantly stressed about the bomb after it had occurred, and spent a great amount of his time partying and making the most out of his life, which was different than most of the characters that were constantly worried about themselves and those around them. Dr. Masakazu Fuiji was chosen in the story Hiroshima for his relaxed nature and his ability to help other patients.
One reason why Dr. Fuiji was chosen