The bombings claimed about 200,000 lives almost immediately, with the death toll continuing to rise over the decades due to radiation-related sickness.
This week marks the start of a significant period for Japan. A whirlwind of events to mark the passing of seven decades since the bombings is followed by the anniversary of the end of the war on August 15.
There will be numerous memorial services in addition to countless peace concerts and exhibitions - Yoko Ono will unveil a new peace installation in Hiroshima.
The spotlight will be on Shinzo Abe, the Prime Minister and what he says to mark these occasions - in particular, the anniversary of the end of the war, amid concerns he will trigger tension with neighbours China and South Korea by diluting earlier wartime apologies.
For survivors such as Nakabushi, the anniversary resurrects a catalogue of painful memories - from the horrifying injuries she witnessed to the death of her mother - alongside a strengthened resolve as she grows older to voice her opposition to nuclear warfare.
She attributes a string of fortuitous coincidences - the fact she was inside the kindergarten and protected from radiation , then managed to flee the building before it collapsed - to her survival, despite being only 1.5km from the centre of the blast.
Her mother was not so fortunate. The bomb exploded only 800m from where she was working with neighbours and relatives.
"My mother suffered severe burns to the whole of her body, but she managed to return home," said Nakabushi. "My grandfather told me that after my mother found out that I was alive, she fell unconscious.
"We headed for the suburbs with my mother on a daihachi guruma [a two-wheeled cart] and I will never forget what I saw next. The houses were gone and we saw hundreds of people with burns walking.
"They were covered in ash, from head to toe, their hair was standing on end and burned skin was hanging from various parts of their bodies like used rags. It was like seeing an army of ghosts."
The surviving family members eventually found refuge in a small shelter.
"My mother died beside me, without me noticing, on August 8. I was only 5 and it changed my life."
She sees herself as one of the lucky ones: after living in Hiroshima with her father and stepmother, she married her university academic husband and moved to Osaka at the age of 25, before having three children.
Others were not so fortunate. Women suffered rejection from marriage partners fearful that they would not produce healthy babies, while employers also discriminated against hibakusha.
Nakabushi began talking to children across Japan about her experiences. She highlights a string of statistics, including the fact that the Hiroshima death toll on the day of the bombing was 100,000, doubling to 200,000 within five years, and rising to 247,000 the following year.
Nakabushi is an active member of the Tokyo Federation of A-Bomb Sufferers Organisation.
When asked if she still feels some bitterness, she replies: "Of course I do. There's nothing more catastrophic than what we experienced.
"It goes without saying that atomic weapons are absolute evil. War takes innocent victims on both sides. Being at peace is the happiest and most precious thing for humankind."T
