Around 150 people, like Uragashira, are thought to have been exposed to both bombings.
The only person officially recognized as a survivor of both bombs, Tsutomu Yamaguchi, who died in January aged 93, once told an interviewer: "I thought the mushroom cloud had followed me."
Media interest has grown in the double-survivors. Last month, a publisher released the Japanese translation of interviews a New York Times correspondent held with nine of them in the 1950s.
Film director Hidetaka Inazuka has recorded testimonies by double bomb survivors to keep alive their memories.
While many Americans believe the bombs were necessary to bring a speedy end to the war, Inazuka, like many Japanese, argues the attacks -- at least the one on Nagasaki -- were unwarranted because Japan was on the verge of surrender.
"Hiroshima was completely destroyed, which should have been sufficient," Inazuka said. "We need to strictly verify why they were dropped on the two cities."
Inazuka said the clock is now ticking to record the voices of the survivors, whose average age is above 75, saying: "Their children or grandchildren need to take the baton as we only have 10 years or so left."
Many single and double "hibakusha" -- atom bomb survivors -- have long kept silent, fearing discrimination against them or their offspring, but many have now started speaking out about their traumatic memories.
"I didn't tell anyone before that I'm a hibakusha because I thought no one wants to marry a person like me," said another survivor of both attacks, 80-year-old Misako Katani.
"Bodies were everywhere in the city," she said about Hiroshima. "Some were skeletons and others were bloated from the black rain."
She remembers the feel of the ashes of her 14-year-old sister, whose human shape remained recognizable in their charred family home, where the remains of their mother were also found.
Katani was told by her father to bring the ashes to their ancestors' graveyard in Nagasaki, where she was exposed again -- a double dose that she said caused her to fall into a three-day coma, bleed and lose her hair.
"The atomic bombings destroyed my life," Katani said. "I heard that President Obama wants to make a visit, but just a visit doesn't mean much. I hope he will pledge to create a world without nuclear weapons."