The United States Embassy in Japan referred all requests for comment to Washington, and on Friday, the White House spokesman, Patrick Ventrell, said that “Ambassador Kennedy is doing a great job representing the United States in Japan.” The State Department said that even before Ms. 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 posting on Twitter, an official said.

Commentators in Japan say some of the turbulence may be inevitable, since the Obama administration chose in Ms. 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 officials felt jittery with her approach, it might prove difficult for them to say so publicly.

Image Ambassador Caroline Kennedy with Foreign Minister Fumio Kishida in Tokyo on Friday. Credit... Yoshikazu Tsuno/Agence France-Presse — Getty Images

“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 Ms. 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.

The Kyodo news agency of Japan, in its headline, quoted the Yonhap news agency of South Korea as saying that the two ambassadors 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 touchy issues may prove a particular headache for the government of Prime Minister Shinzo Abe, a conservative who has pledged to maintain close ties with Washington. Mr. Abe, who has 260,000 followers on Twitter, has been popular in Japan’s small but very vocal community of nationalist Web users.