Mr. Tanimoto cooked his own breakfast. He felt awfully tired. The effort of moving the piano the day before, a sleepless night, weeks of worry and unbalanced diet, the cares of his parish—all combined to make him feel hardly adequate to the new day's work. There was another thing, too: Mr. Tanimoto had studied theology at Emory College, in Atlanta, Georgia; he had graduated in 1940; he spoke excellent English; he dressed in American clothes; he had corresponded with many American friends right up to the time the war began; and among a people obsessed with a fear of being spied upon—perhaps almost obsessed himself—he found himself growing increasingly uneasy. (1.4)
There was apparently a whole bunch of paranoia regarding foreigners leading up to (and following) the dropping of the bomb. Unsurprisingly, people like Mr. Tanimoto, who had an affinity for America and had traveled there, seemed to attract that kind of sentiment.
To Father Kleinsorge, an Occidental, the silence in the grove by the river, where hundreds of gruesomely wounded suffered together, was one of the most dreadful and awesome phenomena of his whole experience. (2.47)
In addition to reflecting on the suffering of the people around him, Father Kleinsorge seems to have noticed a cultural difference in how the "non-Occidentals" (i.e., non-Westerners) suffered in silence.
A few minutes later, a band of soldiers came up, and an officer, hearing the priests speaking a foreign language, drew his sword and hysterically asked who they were. One of the priests calmed him down and explained that they were Germans—allies. The officer apologized and said that there were reports going around that American parachutists had landed. (3.11)
It seems the paranoia about foreigners persisted after the worst had happened, as rumors swirled around. Even Germans, who had fought on Japan's side in the war, were subject to it if they were perceived as looking like Americans…
The woman's gentleness made Father Kleinsorge suddenly want to cry. For weeks, he had been feeling oppressed by the hatred of foreigners that the Japanese seemed increasingly to show, and he had been uneasy even with his Japanese friends. This stranger's gesture made him a little hysterical. (3.35)
Father Kleinsorge had apparently been dealing with a lot of xenophobia/anti-foreigner sentiment leading up to the blast, even though the Germans and Japanese were war allies.
While he was at work, a Miss Tanaka came and said that her father had been asking for him. Mr. Tanimoto had reason to hate her father, the retired shipping-company official who, though he made a great show of his charity, was notoriously selfish and cruel, and who, just a few days before the bombing, had said openly to several people that Mr. Tanimoto was a spy for the Americans. Several times he had derided Christianity and called it anti-Japanese. […] Now he was very weak and knew he was going to die. He was willing to be comforted by any religion. (3.46)
Despite the fact that Mr. Tanaka had been spreading all kinds of rumors about Mr. Tanimoto, claiming that he/his religion were anti-Japanese, he ended up asking for Mr. Tanimoto's help when he found out he was dying.
For ten days after the flood, Dr. Fujii lived in the peasant's house on the mountain above the Ota. Then he heard about a vacant private clinic in Kaitaichi, a suburb to the east of Hiroshima. He bought it at once, moved there, and hung out a sign inscribed in English, in honor of the conquerors: M. FUJII, M.D. MEDICAL & VENEREAL (4.19)
Like Mr. Tanimoto, Dr. Fujii had some distinct pro-Western sentiments, and Hersey makes several references to how much he loved entertaining the "conquerors" and keeping up his foreign languages. He also ended up having a big fun (no, really, it sounds like it was awesome) trip to the States later in life.
The scientists had these and other details which remained subject to security in the United States printed and mimeographed and bound into little books. The Americans knew of the existence of these, but tracing them and seeing that they did not fall into the wrong hands would have obliged the occupying authorities to set up, for this one purpose alone, an enormous police system in Japan. Altogether, the Japanese scientists were somewhat amused at the efforts of their conquerors to keep security on atomic fission. (4.25)
Apparently there was some tension between the occupying American forces and Japanese scientists who were (understandably) trying to figure out the nature of the bomb that had been dropped on their country. Apparently, the fact that the U.S. would try to keep the secrets of atomic fission under wraps in the country where it was unleashed was a source of ironic amusement for the scientists.
"If a Japanese hears the words "tenno beika" [His Majesty the Emperor], it is different from a Westerner hearing them—a very different feeling in the foreigner's heart from what is felt in the Japanese person's heart." (5.70)
This is Father Kleinsorge describing the unique power hearing the name of the Emperor has for a Japanese person, as opposed to anyone else. Even if those words don't have the same meaning for him as a foreigner, it's telling that Father Kleinsorge seems willing/able to try to understand that emotion.
He had the body taken to a crematorium; then, that night, it was taken out a back way and was delivered to the American-run Atomic Bomb Casualty Commission, on top of a hill to the east of the city. […] He was shown that his father's brain had atrophied, his large intestine had become enlarged, and there was a cancer the size of a ping pong ball in his liver. (5.123)
It's interesting to note that the organization in charge of monitoring the lasting impact of the bomb/its effects was American-run.
After that, Chisa Tanimoto trotted onstage with clipped steps, because she was wearing what she never wore at home—a kimono. (5.170)
When Mr. Tanimoto was tricked into being a guest on "This Is Your Life," apparently the show runners asked her to come out in a traditional kimono, despite the fact that this garb was not typical for her. Hmm, wonder why they wanted her in something like that?