TOKYO — The last time the sister of a future emperor of Japan got married, thousands of well-wishers lined the streets as the bride, Princess Sayako, left the palace to attend the ceremony and reception at one of Tokyo’s premier hotels.
But when Princess Mako, 30, a niece of the current emperor and an older sister of the likely future sovereign, married on Tuesday, there was just a simple trip to a registry office in Tokyo, handled by royal representatives.
Still, even without a televised wedding or a balcony kiss, there was a poignant expression of romantic devotion. In a formal news conference on Tuesday afternoon, the groom, Kei Komuro, looked into the camera and declared: “I love Mako. I would like to spend my one life with the person I love.”
The path to that tender moment had been torturous. Not long after the princess and Mr. Komuro announced their engagement four years ago, the public began to question her choice. Tabloids revealed that his mother had received 4 million yen, or about $36,000, from an ex-boyfriend whom she had not repaid, leading critics to suggest that Mr. Komuro was trying to marry into the imperial family for money or fame.
Princess Mako’s father withheld approval of the marriage, citing the curdled public opinion. The paparazzi chased Mr. Komuro, 30, after he left for New York to attend Fordham Law School and tracked his shaggy hair and food truck habits. Savage attacks on social media left the princess suffering from post-traumatic stress disorder.
When Mr. Komuro returned to Japan late last month to quarantine before the marriage, the scrutiny grew even more frenzied, bordering on the absurd. The media and the public were shocked, simply shocked, by the fact that he arrived from New York sporting a ponytail. One tabloid weekly reported that a royal court official had sneered at Mr. Komuro’s choice to wear a pinstripe suit — as opposed to one in solid black or navy — to meet his future in-laws. In some surveys, as many as 80 percent of respondents have said they opposed the marriage.
Yet after waiting three years for Mr. Komuro to finish law school and start a job at a New York law firm, the patient couple, who were college sweethearts at the International Christian University in Tokyo, registered their marriage on Tuesday morning.
At the news conference, held at a hotel less than a mile from the Imperial Palace, the couple sat side by side at a long table and faced a roomful of reporters and a phalanx of cameras. The bride wore a pale blue sheath dress and jacket with a single strand of pearls, while Mr. Komuro wore a dark navy-blue striped suit.
In prepared remarks, the princess said: “I acknowledge that there are various opinions about our marriage. I feel very sorry for the people to whom we gave trouble. I’m grateful for the people who have been quietly concerned about us, or those who continued supporting us without being confused by baseless information.”
To avoid having to answer unpleasant questions or address falsehoods, the couple asked to reply in writing to five questions from reporters submitted in advance. To avoid accusations that they were wasting taxpayers’ money, they paid to rent the room for the news briefing.
Underlying many of the virulent opinions about Princess Mako’s choice of partner is a strain of existential panic about the royal family, which stands as a symbol of traditional Japan. The world’s oldest monarchy faces a looming succession crisis, and the princess’s marriage highlights a problem that the government has declined to address.
Under the Imperial Household Law, which governs the succession of Japan’s emperors, women are not allowed to reign on the throne. The law also stipulates that Princess Mako must relinquish her royal title because she is marrying a commoner, and she will become a commoner herself. Any children she has will not be in line to the throne.
A vast majority of the Japanese public thinks the law should be amended so that women — including Princess Aiko, the 19-year-old daughter of the current emperor, Naruhito — can sit on the throne. A recent survey by Kyodo News showed that about 80 percent also want children born of royal women like Princess Mako to be in the line of succession.
So far the conservative wing of the governing Liberal Democratic Party has staunchly opposed any changes that would allow women to reign or children of royal women to join the line of succession.
But the family is running out of male heirs, with just three left who can succeed the current monarch: Emperor Naruhito’s 85-year-old uncle; the emperor’s 55-year-old brother, Akishino, Princess Mako’s father; and the emperor’s 15-year-old nephew, the younger brother of Princess Mako and the only family member of his generation eligible to serve as emperor. (By contrast, the British royal family has more than 20 people in line to the throne, many of them female and none of them — yet — octogenarians.)
The possibility that the political establishment may have to bow to popular opinion or demographic reality means the public feels entitled to weigh in on Princess Mako’s choice of husband, in case she is reinstated into the imperial family.
“As we don’t know yet whether female members of the family might be allowed to head a line of succession or succeed to the throne, people care so much about her marriage,” said Hideya Kawanishi, associate professor of modern history and an expert on Japan’s imperial system at Nagoya University.
The public has found Mr. Komuro unsuitable mainly because of suspicions about his family. His mother was widowed when his father died and then was entangled in a relationship with a man who later accused her of not paying back the $36,000 debt. Mr. Komuro and his mother say they believed the money was a gift, but after the public uproar, Prince Akishino asked Mr. Komuro to explain the situation. He delivered a 28-page document earlier this year detailing the financial arrangement and how it would be resolved.
At Tuesday’s news conference, Mr. Komuro addressed the controversy directly, explaining that his mother suffered from mental illness and that he had offered a settlement to her ex-boyfriend.
The whole contretemps has left a lingering distrust of his family in the public’s mind. In Japan, “marriage is still a marriage between families,” said Michiko Ueda, associate professor of political science at Waseda University in Tokyo.
Rumors have metastasized and now impugn Mr. Komuro’s character. Critics on social media have branded him a gold digger or a grifter. The media suggested that a biography, posted on the website of Lowenstein Sandler, the law firm where he works in New York, listed awards that were fabricated. A spokesman for Fordham Law School confirmed that Mr. Komuro did in fact earn the awards he listed.
Royal watchers say that Mr. Komuro falls short of traditional expectations for Japanese men and that his treatment reflects suspicion of the outside world.
“Part of it is that Mr. Komuro was not very submissive to Japanese values because he went to international school, is a fluent English speaker and quit a Japanese bank,” said Kumiko Nemoto, a professor of sociology at Kyoto University of Foreign Studies.
“In Japanese society, people like to see that people are sacrificing part of themselves to society and the group and family,” Ms. Nemoto added. Mr. Komuro, she said, is more “individualistic, trying to prove himself by accomplishing something professionally.”
Now that they are married, the princess, who will be known as Mako Komuro, may move to New York to join her husband. She has turned down a royal dowry worth about $1.4 million, so the couple will have to live off Mr. Komuro’s salary at first.
The princess holds a master’s degree in art museum and gallery studies from the University of Leicester in Britain and has worked at a museum in Tokyo for more than five years, so she may be able to find a job in New York’s art world.
Perhaps it is the couple’s decision to carve out their own life outside Japan that has invited the most public vehemence. Even if she must leave the family, the princess is expected to conform to traditional notions of duty.
“The imperial family used to be looked at like gods, beautiful and unreachable, but that is no longer the case,” Hanako Onodera, 59, said while walking with two friends in the imperial palace gardens last week.
“Maybe this generation now dares to speak out more and demand what they want more than the generation before,” she added. “They don’t feel as much pressure to put the country’s needs before their own.”
In response to a question from a reporter on Tuesday afternoon, the new Mrs. Komuro said that she had no plans to give media interviews and that she hoped “just to lead a peaceful life in my new environment.”
Hikari Hida contributed reporting.