HIROSHIMA, Japan — After 18 years of almost daily lectures about surviving the atomic bomb dropped here on Aug. 6, 1945, Setsuko Iwamoto’s stories to classrooms full of students have a finely limned quality about them, as smooth as pebbles in a creek.

There is no straining for melodrama as the 71-year-old woman recounts how her skin seemed to melt and pour off her arms after the flash, or how whatever scraps of cloth that could be found were used by people to protect themselves from the black rain that fell afterward.

Stories of survival do not get much more compelling. But Ms. Iwamoto worries now, with Japan inching toward rearmament, that the spirit of Hiroshima and the moral power of her story are fading.

Each year, she said, the stares of the students she faces from the podium grow blanker, just as their questions about the atomic bombing grow more stilted, appearing rehearsed rather than heartfelt.

“Just a few years ago, most schoolteachers had direct memories of the war,” said Ms. Iwamoto, who said she was found to have cancer last year but appeared hale. “That’s not the case at all anymore, though, and I wonder once this kind of lecture ends, how effectively the experience of war is taught.

“In my day we had trouble just surviving every day, whereas these days everyone in Japan is comfortable,” Ms. Iwamoto added. “Children learn about war through manga [comic books] and think it is kind of cool. They have no particular sensation of Japan’s defeat.”

The profound shock of the Hiroshima bombing, and that of Nagasaki three days later, is widely credited not only with ending World War II, but with creating a strong emotional underpinning to Japan’s official creed of nonviolence, consecrated in an American-drafted Constitution that faces increasingly strident calls for revision.

Fears about Japan becoming increasingly blasé about remembering the atomic bombings, though, are not limited to the survivors, or hibakusha, as they are known here.

Hiroshima’s entire image and economy are linked to the horrendous final days of World War II, and city officials say visits by Japanese travelers are locked in a serious, long-term decline, broken only by a modest spike since the Sept. 11, 2001, terrorist attacks in the United States.

Commissions have been formed to reverse the trend. A museum on the grounds of the Peace Park, near ground zero, has been expanded and modernized. In the hope of popularizing visits here, even a manga has been created — to celebrate the memory of Sadako Sasaki, a 12-year-old who died of blood cancer years after the bombing.

“We are faced with the challenge of conveying this experience to the next generations,” said Noriyuki Masuda, associate director of the Hiroshima Peace Memorial Association. “At some point we realized that what we had was a crisis involving young people’s consciousness. We have been facing a change in attitudes and a decline of interest in Japan as a nation.”

When Ms. Iwamoto completed her one-hour presentation to a lecture hall full of sixth graders who had come to Hiroshima on a field trip, five minutes were left for what was billed as a question and answer session.

In lieu of a question, a young girl who appeared to have been chosen for her excellence in study walked nervously to the microphone and read a brief speech in the name of her class. “Why must there be war?” she said flatly, ending her comments with a wish for the lecturer’s good health.

Asked if visits at a slightly older age might favor deeper thought, not to mention real questions, the girl’s teacher, Keiko Tokunaga, demurred. “This is the age when children are just beginning to think about the world,” she said, “and I think that it is the best time to introduce ideas like this. But this is just a start.”

Out on the grand plaza of the Peace Park, where the famous atomic bomb dome sits, just a stone’s throw across the Motoyasu River, one has trouble imagining that visits to the Hiroshima memorial grounds are in decline.

Over the course of a fine spring day, one group after another of uniformed students troops from the museum to the dome, typically laying wreaths and garlands of origami cranes by a statue of Miss Sasaki, the renowned 12-year-old bomb victim.

Foreign visitors, whose numbers have increased as those of Japanese have declined, are also constantly in evidence. This day, a group of volunteer greeters were excitedly awaiting the arrival of a group from Senegal, including the country’s ambassador.

At the approach of an American journalist, a group of ninth graders from Tokyo was unfailingly polite, and even excited to be answering questions about their trip here. None had discussed the bombing, or Japan’s long-fixed identity as a nation of peace, with their parents before coming.

Nor did they have many ideas of how the war began or why it ended amid mushroom clouds and hundreds of thousands of instant casualties. “This was kind of an experiment, because it was the first atomic bombing,” said Eiichiro Hiraka, a 14-year-old with a dream of becoming a professional baseball player. “Hiroshima was the perfect size for that.”

A classmate, Kaoru Iwasaki, said she had studied World War II the year before but did not remember much. “I’m sorry, but I can’t tell you why the war started,” she said. Asked the same question, her friend Chisato Kajitani declared that she was not very interested in the subject. “I’ve never really thought about that question before,” she said.