Answer:
She had no burns and only minor external wounds. She was quite all right for a while. But on the 4th September, she suddenly became sick. She had spots all over her body. Her hair began to fall out. She vomited small clumps of blood many times. I felt this was a very strange and horrible disease. We were all afraid of it, and even the doctor didn't know what it was. After ten days of agony and torture, she died on September 14th.
=One Hiroshima survivor described the death of her daughter from radiation sickness.=
This explains it.