A Princess Is Set to Be Wed. But It’s No Fairy Tale.

TOKYO — Anyone who dreams of being a princess should probably have a chat with Princess Mako of Japan.

On Friday, the agency that manages the affairs of Japan’s royal family announced that the princess, the 29-year-old niece of Emperor Naruhito, would marry her fiancé, a commoner named Kei Komuro, on Oct. 26.

It’s a long time coming. The couple, who first met in college, have been engaged since 2017 — but getting to the chapel has meant running a bruising gauntlet of media scrutiny and savage public commentary on Mr. Komuro’s fitness to be the spouse of an imperial daughter.

The pressure on the couple has been so intense that the princess has been diagnosed with post-traumatic stress disorder, Japan’s public broadcaster, NHK, reported.

No Horse, No Carriage

If you’re expecting pomp and circumstance, prepare to be disappointed. There will be no royal wedding. Instead, Princess Mako intends to renounce her royal heritage and settle into a normal life in New York, where Mr. Komuro, 29, works in a law office after studying at Fordham.

It’s hard to blame her. Her engagement has been endlessly and disapprovingly dissected, and her family, citing negative public opinion, has expressed little public support for the match.

The couple’s wedding, originally planned for 2018, was pushed back after news reports that Mr. Komuro’s mother owed $36,000 to a former fiancé. Some of that money, the press said, had been used to pay for Mr. Komuro’s schooling.

The affair led to insinuations that Mr. Komuro was a gold digger, an image that he struggled to shake off.

At the urging of his future father-in-law, Crown Prince Akishino, he released in April a 28-page document explaining the loan, and his lawyer later vowed that Mr. Komuro would pay it back. But the damage was long since done.

Harry and Meghan They Aren’t

Japan’s staid royal family is low on star power and has largely avoided the dramas surrounding the British royals.

The family, the world’s oldest royal line, has served only in a ceremonial capacity since the end of World War II, and it tends toward carefully managed appearances and oblique statements.

Princess Mako and Mr. Komuro are unlikely to appear with Oprah Winfrey or get a Netflix production deal, as did the world’s most famous royal renouncers, Prince Harry and Meghan Markle.

Hungry for gossip, Japanese tabloids find chum in even the smallest issue.

The most recent scandal is about a ponytail. After Mr. Komuro, who had last been seen with a mid-length boyish coif, was sighted in New York sporting long hair tied in the back, his new look became front-page news.

The tabloids ran photos of Mr. Komuro’s head from every angle. Japanese Twitter exploded with scathing comments, and newscasters tut-tutted the hairstyle as unbecoming of a princess’s beau.

Keep Your $1.4 Million

Seemingly fed up even before the latest hullabaloo, Princess Mako has reportedly decided to give up all of the trappings of royal life.

Even in the happiest case, Japanese law decrees that women who marry commoners are to be pruned from the family tree. No woman may sit on the Chrysanthemum Throne, which must be occupied by a man from the male line of succession — currently, only the crown prince and his son qualify.

The same laws that will force Princess Mako out of the royalty also entitle her to official ceremonies marking her departure and a dowry of around $1.4 million to start her new life.

Princess Mako will forgo both the ceremony and the payment. She is the first in Japan’s royal family to do so since the end of World War II.

Instead, the couple will register their marriage in Tokyo and retreat later this year to New York, where Mr. Komuro recently began work at the Manhattan law firm Lowenstein Sandler and is awaiting his results on the New York bar exam.

Princess Mako, who holds a master’s degree in art museum and gallery studies from the University of Leicester in Britain and is pursuing a doctoral degree at the International Christian University in Tokyo, has not announced her plans, although there has been speculation that she could find work in New York’s art world. She has spent the last five and a half years working at a museum at the University of Tokyo.

Running for the Exits

The princess is far from the first woman to have sought an escape from the royal microscope.

Empress Masako, a former diplomat educated at Harvard and Oxford, famously shied from the public spotlight and intense scrutiny about whether she would produce a male heir.

Princess Mako will be the ninth woman from the Japanese royal family to marry a commoner since new laws governing the royal family came into effect after World War II.

In a 1965 interview with The Asahi Shimbun, a Japanese newspaper, Takako Shimazu, the youngest daughter of Japan’s wartime emperor, Hirohito, said that she had found peace during two years living in Washington, D.C., where her husband worked as a banker.

“I’m happier than when I lived in Japan,” she said. “As a citizen, there is no mental pressure.”

The most important thing about the change, she said later, was that “I was able to live without garnering people’s attention, quietly.”

Reporting was contributed by Hisako Ueno, Makiko Inoue and Hikari Hida.