Dozens of children bled dark red blood from terrible wounds as they lay along a street of the city of Matsue.

Naofumi Tanaka, 78, has never forgotten the ghastly scene, even over 70 years later.

The children had apparently been evacuated to Matsue, Tanaka's home city in the neighboring prefecture of Shimane, after the United States dropped an atomic bomb on Hiroshima on Aug. 6, 1945 -- the first time a nuclear weapon had been used in warfare.

"I'd never seen people so badly hurt. We must not have war as it victimizes the weak," Tanaka told Kyodo News in a recent interview.

(Naofumi Tanaka)

During the Pacific War when Tanaka was still a boy, almost no-one in his neighborhood had experienced air raids. He spent his days fishing and playing in the nearby Lake Shinji, often staring up at enemy aircraft as they flew overhead without feeling the need to flee.

But, one summer morning, that all changed.

Born into a family that ran a liquor store and a large Japanese sake brewery, Tanaka lived in a house near the Shinji rail station.

When he stepped outside that day after the bomb, he saw injured children lying side by side on futon mattresses stretching about 50 meters down the street.

They had suffered burns to their faces. Pieces of washi, or Japanese paper, were placed on their wounds, apparently as makeshift bandages.

Burns were one of the typical injuries caused by the atomic bomb. The bomb, called "Little Boy" due to its thin shape compared to "Fat Man" which would destroy Nagasaki on Aug. 9, exploded 600 meters above the ground, destroying the city with its blast and heat radiation. The ground temperature at the hypocenter reached 4,000 C.

Many survivors remember victims wandering around the city, craving water as their charred skin hung loosely from their bodies.

The population of Hiroshima at the time was about 350,000, and about 40 percent of residents, approximately 140,000 people, are estimated to have died by the end of 1945.

Three days after the Hiroshima bombing, the United States dropped the second bomb on Nagasaki, a city about 300 kilometers southwest of the first target, killing an estimated 74,000 people.

Many of the atomic-bomb survivors, known as hibakusha in Japanese, suffered from radiation sickness and cancer.

The Japanese government officially designated Hiroshima and Nagasaki residents as hibakusha, as well as babies whose mothers were victims, rescue workers, and others who were irradiated after entering the bombsites within two weeks of the attacks.

As of the end of fiscal 2017, there were still 154,859 people designated as hibakusha, according to the Ministry of Health, Labor and Welfare.

Although the young Tanaka thought the injured children may have been survivors sent from Hiroshima by train, the boy kept his thoughts bottled up for many years.

In 2009, Tanaka's liquor store used the building that had housed the sake brewery as a temporary exhibition site for photos taken before the war, marking the 100th anniversary of the opening of Shinji station.

Among them was a photo showing the brewery's exterior wall adorned with calligraphy made by local children. But Tanaka wanted people to know this was also a place where children had suffered.

For the first time in his life, he wrote about his memories and made a panel to display with the photos. One of his neighbors recalled the "strange smell," which confirmed to Tanaka that the tragedy had not been just a terrible dream.

Every year as Aug. 6 nears, Tanaka recalls the day and the horrible scene.

"It's always the most vulnerable, ordinary people who suffer in war," he said. "If we don't cherish the right to speak up, the horror of war will repeat."