TOKYO » Japan went into a collective swoon two months ago when Caroline Kennedy arrived as the United States’ ambassador. The appointment of someone with such celebrity appeal — who offered a living link to a golden age when America was still reassuringly strong and confident — appeared to be proof that Washington was finally giving Japan the embrace it craved.

When she traveled by horse-drawn carriage to present her credentials to Emperor Akihito, a formality observed by many new ambassadors, thousands of cheering Japanese lined the streets in a rare display of public affection for a diplomatic envoy.

But Kennedy has quickly surprised her Japanese hosts by being undiplomatically frank on delicate issues that many of her predecessors would most likely have shied away from, at least in public. She created a stir this week when she publicly expressed "concern" about a bloody annual dolphin hunt that is widely condemned abroad, but that many Japanese view as a part of their traditional culture.

"Deeply concerned by inhumaneness of drive hunt dolphin killing," Kennedy wrote in a tweet posted Saturday. "USG opposes drive hunt fisheries," she added, referring to the U.S. government’s stance on the hunts, in which dolphins are herded into coves so they can be hacked to death.

The comment, coming soon after her embassy issued a rare criticism of the prime minister for visiting a controversial war shrine, indicated that the often reserved Kennedy might be more of an outspoken envoy than many expected, willing to take on subjects the Japanese prefer to discuss behind closed doors. And she is doing so using a social medium that allows for little of the nuance that shapes formal Japanese diplomatic communication; Kennedy is an active Twitter user, posting in English and Japanese for her 75,000 followers.

Her stark criticism of the hunt comes as the United States is trying to strike a delicate balance — nudging Japan to stop antagonizing its neighbors over their shared wartime history, while also encouraging its support for a stronger American presence in the region as a counterbalance to China.

Japanese officials greeted Kennedy’s comments on the dolphin killings — which the State Department says it supported — with a mixture of irritation and seeming confusion.

Yoshinobu Nisaka, the governor of the prefecture where this week’s hunt took place, said in a news conference that "we live on the lives of cows and pigs. It is not appropriate to say only dolphin hunting is inhumane."

The top government spokesman, Yoshihide Suga, defended the hunt — the same one filmed in the 2009 American documentary, "The Cove" — as being in accordance with international law. But he quickly added that Japan would try to "explain our stance to the United States."

The U.S. Embassy in Japan referred all requests for comment to Washington, and on Friday, a White House spokesman, Patrick Ventrell, said that "Ambassador Kennedy is doing a great job representing the United States in Japan." And the State Department said that even before Kennedy’s confirmation hearing last fall, she received numerous comments about Japan’s dolphin hunting practices and decided she wanted to address the issue. She consulted with the department about the administration’s policies before sending her tweets, an official said.

Commentators in Japan say some of the turbulence may be inevitable, since the Obama administration chose in Kennedy a public figure with the star power to dazzle the Japanese public, but who is also not afraid to speak out. Even if some felt jittery with her approach, it might prove difficult for them to say so publicly.

"How do you rein someone like her in?" said Dave Spector, an American who has worked in Japan for more than 25 years as a television commentator and who has followed Kennedy’s ambassadorship closely. "Her father is on the 50-cents coin, for crying out loud. She is bigger than life."

Her fame is so formidable, he said, that she is vulnerable to people looking for meaning in her every move. On Wednesday, a routine meeting with the South Korean ambassador to Japan generated articles in both countries. The news agencies emphasized that a sore point between the two countries had come up during the meeting.

Japan’s Kyodo news agency, in its headline, quoted South Korea’s Yonhap news agency as saying that the two discussed the so-called comfort women issue, but neither article makes clear if she even made a comment on the matter. Many scholars say the women, tens of thousands of them Korean, were forced to serve in wartime Japanese military brothels, but many Japanese conservatives say they were prostitutes.

Her willingness to engage in such touchy issues may prove a particular headache for the government of Abe, a conservative who has pledged to maintain close ties with Washington. Abe, who has 260,000 followers on Twitter, has been popular in Japan’s small but very vocal community of nationalist Web users.

At least one noted woman also spoke out on the dolphin hunt. A day after the ambassador’s tweet, Yoko Ono published an open letter to the fishermen to stop the killings she said have given Japan a bad name internationally. (Dolphin meat is prized in a limited number of places in Japan, but conservatives bridle at foreign dictates of what Japan should do.)

Despite the kerfuffle, Kennedy remains enormously popular in Japan, Spector and others say. Partly, this is because of the aura here that still surrounds the presidency of her father, John F. Kennedy, for whom many older Japanese feel an almost teary-eyed nostalgia. When Kennedy was named as ambassador, Japanese TV stations repeatedly broadcast images of her as a little girl on her father’s lap, or standing forlornly at his funeral.

Nor has Japan been entirely negative about her outspokenness. Some of the comments posted on Twitter expressed admiration for her as a woman who has the courage to speak her mind in Japan, a nation still dominated by men.

But others quickly criticized her for sticking her nose into something that they say is not her, or any other foreigner’s, business. Some angrily reminded her that American Commodore Matthew C. Perry opened Japan at gunpoint in 1853 to secure ports for American whalers.

"We don’t want to be told such things by Americans who used to kill whales just for their oil," said one user. Another was more succinct: "Stupid woman! Go home!"

Many said the relationship between Japan and the United States is strong enough to endure an honest airing of opinions, and that the number of Japanese who feel strongly about the dolphin hunt is limited in any case.

"Frankly I think it’s good that someone with that kind of credentials can say the kind of thing that others would hesitate to say," said Ellis S. Krauss, a professor of Japanese politics at the School of International Relations and Pacific Studies at the University of California, San Diego. Although the message could possibly have been conveyed more subtly and privately, he said, "It would have gotten less attention if Caroline Kennedy hadn’t said it."

Minoru Morita, a political analyst who runs a think tank in Tokyo, said he does not think the flare-up will have a lasting effect on her popularity. "I don’t think many Japanese felt good about her criticizing Japan’s food culture," he said. "But most Japanese have very fond feelings for her, and for the era of her father, and that won’t go away easily."

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Martin Fackler, New York Times

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