Basically what the title says. What I'm curious about is how average Japanese people responded on the individual level, what changes they would have noticed immediately, and within the coming months/years. What was the zeitgeist in the latter half of the 1940s? How did people reconcile the bombings and the surrender? Was their resistance to the American occupation?
This is already getting too broad but I'm also broadly curious about relief efforts in the two cities, and what life looked like for a survivor over a timeline of years.
In short, they were kept in the dark about what had happened. The subject was taboo and the Americans who occupied Japan didn't want them to talk about it.
In the Aftermath of the nuclear bombings of Hiroshima and Nagasaki the Japanese government was able to piece together what happened because they were able to call upon their own nuclear experts who clued them into the types of bombs that had been dropped on the country . For further reading on this topic I suggest that you try and get your hand on a copy of the book, Secret Weapons and World War II: Japan in the Shadow of Big Science by Walter E. Grunden.
However when it came to the popular people's conception of what had happened, it was taboo for the people to discuss it. A good book on the subject of immediate post war Japan would be "When Empire Comes Home: Repatriation and Reintegration in Postwar Japan", by Lori Watt, those that did survive were treated as if they had the plague and were shunned by their family members, Women couldn't find men to marry because of the misconception of what it meant to be a survivor of the nuclear bombings, somehow as if they would kill those around them. And this wasn't just the case for those that survived the Nuclear Bombings, the book also deals with the Japanese that had been living abroad in Japan's empire, and those soldiers that had been captured as prisoners of war by the Soviets. The Repatriation problem was long and arduous and very contentious.
Also there was the American moratorium on talking about the bombings, in the USA we tend to talk about it more frequently now, but at the time the Nuclear bomb was just another bomb, albeit bigger and more deadly, but its effects were not understood widley. There was a married couple that were artists who starting in the 1950's began to draw paintings about what they had witnessed in Hiroshima when they had gone to provide aid to the cities in the aftermath of the bombings. Maruki Iri and Maruki Toshi painted a series of 15 paintings known as the Hiroshima Panels, that depicted the horrific scenes of the aftermath of the bombings. They became prominent anti-war and anti-nuclear activists and their defiance of the taboo caused them to become popular as their depictions were among the few ways that one could see what the bombings had done.