Masahito Hirose was 15 years old when the atomic bomb was dropped on Nagasaki. During the war he worked in the office of the Mitsubishi shipyard factory.
Masahito Hirose lost his cousin in the Nagasaki blast
In the early morning of 9 August, 1945, an air raid warning was issued at about 8 o'clock, but as no planes appeared in the sky above Nagasaki, the alarm was cancelled about an hour later.
So most citizens came out of air raid shelters, children rushed out of caves and housewives started to queue up outside shops to draw their rations of rice.
Many people started work in factories, hospitals and company buildings.
At about 11 o'clock I was working in the office of the factory as usual.
I suddenly saw a white-blue flash and then a sound came - it hit me. I threw myself to the floor and covered my eyes with three fingers, ears with my thumbs and nose with my little fingers, as I'd been taught by my teacher. The next moment many pieces of glass fell down on my back.
After a while all became quiet. I got up and rushed out of the office. Suddenly I saw a cloud climbing up above the northern district of Nagasaki. I could see this gigantic cloud climbing up and up like a tornado. I didn't know what to do so I stood there for a long time, looking at the cloud.
My house was about 3.1km (2 miles) from the bomb's hypocentre.
Mr Hirose still lives in Nagasaki
That morning I'd left the house with my cousin. He was 19 years old. He had left his own house in Osaka [after it was bombed] and came to live in my house in May of that year.
I left the house with him at about 7 o'clock. I parted with him - and he turned right, towards his factory, which was near the hypocentre.
That night he did not come home. But we could not go and find him in the northern part of the city.
On the afternoon of 10 August, his mother left the house to look for him. That night she came back and said: 'I didn't find him anywhere. Around his factory everything has been destroyed and I couldn't find the factory.'
She went out to look for her son the next day and the next day, and she continued to go out to look for him.
On the morning of 15 August she couldn't get out of bed. She had a high temperature and she was bleeding from her nose.
She died crying her son's name.
This interview is from the series 'August 1945', from 3-14 August on BBC Radio 4, at 8.55 BST Mondays-Saturday, and at 9.55 BST on Sunday.