The family's nanny gently informed Caroline that her father had been shot "and they couldn't make him better". With that, Caroline's world was shaken, not for the first time or the last.

Three months earlier, her little brother, Patrick, had died shortly after birth. Then Robert F. Kennedy, the uncle who stepped in to serve as a sort of surrogate father after JFK's assassination, was himself shot and killed five years later.

After losing her mother, Jacqueline Kennedy, to cancer in 1994, Caroline lost her brother John in a 1999 plane crash at the age of 38. Over the years, she has gradually edged back into the spotlight, and stepped more deeply into politics. Early in 2008, she endorsed Barack Obama in the United States presidential campaign, a pivotal moment in his primary race against Hillary Rodham Clinton; Kennedy later served on the team that helped Obama select his running mate.

But she abruptly withdrew after flirting with the idea of seeking appointment to the Senate seat vacated when Clinton became secretary of state, citing personal reasons.

Kennedy had been harshly criticised for giving halting interviews and limiting her interactions with reporters, and some critics questioned whether her background had prepared her for the Senate.

Kennedy seemed far more comfortable with the job description when Obama last summer nominated her to serve as US ambassador to Japan. She was unanimously confirmed by the US Senate in October.

In Tokyo on Tuesday, thousands of onlookers snapped pictures and waved to Kennedy as she travelled by horse-drawn carriage to the Imperial Palace to present her credentials to Japan's emperor. She was one of several foreign envoys to make the journey. But the crowds had eyes for only one. Well-wishers shouted "Kennedy-san! Kennedy-san!" as the procession weaved its way along the streets.

The procession was accompanied by palace officials in European-style ceremonial costumes, including a footman in breeches. Kennedy's carriage, the spokes of its coppery wheels gleaming in the late afternoon sunshine, was led by a horseman astride a white horse.

In an unusual move, national broadcaster NHK showed Kennedy's arrival at the palace live.

"Honoured to present my credentials to His Majesty the Emperor of Japan. What a memorable day!" Kennedy tweeted later, sharing a photo of her alighting from the carriage at the palace's Pine Hall.

Speaking to reporters, Kennedy described the ceremony as "wonderful". "I am honoured to serve my country," she said.

Kennedy is the first female US ambassador to the Asian giant, which consistently ranks lower than other wealthy nations on women's empowerment in politics and business. Her appointment has been hailed in Japan, although some critics have voiced concern at having a diplomatic novice in the important post at a time of high tensions between Japan and a rising China. Japan is the United States' fourth-largest trading partner and home to the Navy's 7th Fleet and 50,000 American troops.

"It is a special honour for me to be able to work to strengthen the close ties between our two great countries," Kennedy said upon her arrival in Japan on November 15. "Our alliance is critical to a prosperous and peaceful world."

Such weighty matters do not explain the huge turnout that greeted her on Tuesday, however. It was a rare display of public affection for a foreign dignitary in Japan.

"I'm very excited to have seen her because I was a big fan of her mother Jacqueline-san," gushed Shizuko Harada, 68, who was among thousands of onlookers.

The crowds in Tokyo are indicative of an enduring fascination with the Kennedy clan that transcends borders and persists half a century after her father's murder.

Through it all, level-headed Caroline soldiered on, lending her support to the causes and ideals her parents and brother had championed. She's served as president of the John F. Kennedy Library Foundation and chaired the senior advisory committee of the Institute of Politics at Harvard, set up as a memorial to her father.

Trey Grayson, director of the institute, describes Kennedy as quiet and down to earth, willing to be blunt when needed, and gracious at managing the daily challenges that come with nurturing her father's legacy.

"Every day, people walk up to her and say, 'I'm such a big fan of your father, he inspired me to do this,' and she's handled that so well," Grayson said.

Asked in 2012 if she ever felt overwhelmed by the legacy of the Kennedy years and the carefully cultivated image of a modern day Camelot, Kennedy said simply: "I can't imagine having better parents and a more wonderful brother. So I feel really fortunate that those are my family, and I wish they were here.

"But my own family, my children, my husband, are really my real family and so ... we're just us."

Raised in privilege on New York's Upper East Side, Kennedy earned a Columbia law degree, but rather than practice law she chose to write and edit books about poetry, the right to privacy and other subjects.

While her brother made a public splash and earned the label "sexiest man alive" from magazine, Caroline limited her public appearances and tried to be just another parent shepherding her kids to adulthood, working as an unpaid fundraiser for the city's school system once they got older. She is married to exhibit designer Edwin Schlossberg, who has joined her in Tokyo.

For all the days that felt just ordinary, though, there were moments when recollections of the trials of her life would come crashing through.

"You don't think about it all the time," Kennedy once said, in a comment cited in Christopher Andersen's biography . "Sometimes you're just walking down the street and it just hits you ..."