TOKYO — A royal engagement typically unleashes breathless headlines and frenzied efforts by the press to learn of the wedding details. All that is happening in Japan, where Princess Mako, the eldest grandchild of Emperor Akihito, will soon be engaged to her college boyfriend.
But news of the impending engagement, which broke Tuesday night, is also raising fresh questions about the status of women in the imperial family.
Under the Imperial Household Law, which governs the succession of emperors in Japan’s monarchy, the world’s oldest, women are not allowed to reign on the throne. And women born into the royal family must officially leave it once they marry.
So when the princess, a 25-year-old doctoral student at International Christian University in Tokyo, marries Kei Komuro, 25, an aspiring lawyer, she will become a commoner, narrowing the prospective pool of heirs to the throne.
As Japan considers whether to reform the imperial law to accommodate the current emperor’s request to abdicate before he dies, many Japanese have suggested it is time to revise the 70-year-old law to allow women to ascend to the throne and to allow royal daughters to bear heirs.
With so few males left in the imperial family — there are only five, including the current emperor — Japan’s monarchy is facing a looming succession crisis.
The public overwhelmingly supports changing the law not only to allow the emperor to give up the throne, but to allow female successors. In a poll by Kyodo News this month, 86 percent of those surveyed said they were in favor of allowing a female to reign. And close to two-thirds said that sons — or daughters — born of royal women should also be allowed to ascend to the throne.
Under the current law, even if the princess, the eldest daughter of Prince Akishino, the younger brother of Crown Prince Naruhito, were allowed to remain within the imperial family after she marries, her children — even any sons — would not be in line to the throne. That is because the law requires that the line of succession pass only through the men of the family.
On Friday, Prime Minister Shinzo Abe’s cabinet is expected to introduce a one-time bill to allow Emperor Akihito, 83, to give up the throne, opening the way for Prince Naruhito, 57, to take over before his father dies.
The legislation, which will need to be approved by the Parliament, does not address the issue of female succession, or the question of whether the children of royal women will be allowed to ascend to the throne.
After Prince Naruhito, his immediate successor would be his younger brother, Prince Akishino, 51, since Prince Naruhito’s only child is a daughter, Princess Aiko, 15. Prince Akishino would be followed by his son, Prince Hisahito, 10, the younger brother of Princess Mako. Prince Hisahito is the only boy of his generation in the imperial family.
Given how short the line of succession has become, imperial family watchers say that the law should be reformed to allow for more heirs.
“Now we all know that an important imperial family member will be lost with the engagement of Princess Mako,” said Isao Tokoro, professor emeritus of legal history at Kyoto Sangyo University and an expert on the imperial family system. “It is urgent that the system should be reformed so that female members can remain in the imperial family. Otherwise, we will lose more and more members from the imperial family.”
Mr. Tokoro added that Japan has previously had eight female emperors who “did wonderful jobs.” The current law prohibiting female succession has been in place since 1947, when the postwar Constitution downgraded the emperor to a symbol of Japanese unity from a god.
Twelve years ago, Princess Mako’s aunt, Princess Sayako, now 48, the only daughter of Emperor Akihito, married a commoner and left the imperial household. In doing so she gave up a royal allowance, though she gained the right to vote — and pay taxes. She never had children.
Princess Mako, who has a master’s degree from the University of Leicester in England, will also gain those rights when she marries Mr. Komuro. According to news media reports, she has been dating him since 2012, and her parents have already approved the engagement, which will be officially announced soon
Conservative supporters of Mr. Abe are steadfastly opposed to allowing women on the throne, or even sons of female family members. Yet their insistence on male lineage is threatening the future of the royal bloodline.
The opposition Democratic Party has called for a revision that would allow women to take the throne or to stay in the family after marriage. In remarks to reporters on Wednesday, Renho Murata, the Democratic leader, said her party was “urging the government, based on a consensus of the public, to set a deadline to study establishing female imperial branches.”
Analysts said that Mr. Abe’s silence on women in the imperial household was particularly striking given his professed support for women’s equality.
“Mr. Abe has tried to showboat as somebody who embraces ‘womenomics’ and promotes empowerment of women,” said Jeff Kingston, the director of Asian studies at Temple University in Tokyo. “But here is a chance for him to step up, and instead he is avoiding making a decision that would benefit the imperial institution. He feels that this is a step too far, so clearly there is a glass ceiling at least as far as the imperial household is concerned.”