PEOPLE Explains: Why Women In Japan's Imperial Family Must Give Up Their Royal Status to Marry Commoners

If a female member of the Japanese imperial family wishes to marry a commoner, she often must make a seemingly impossible choice. If she marries the person she loves, she will lose her royal status and position in her family.

Princess Mako is the latest royal to announce her intention to marry her commoner fiancé and lose her place in the imperial family. She officially announced her engagement to her university boyfriend Kei Komuro in September 2017. But this week, the couple said they decided to postpone their wedding until 2020 due to “immaturity,” meaning Mako will remain a princess until then.

Though to be oldest hereditary royal family in the world going back 1,000 years, the Japanese Imperial Family is still steeped in tradition. And one of said traditions is not allowing female members of the family to remain official members if they marry someone who does not have an aristocratic or royal background. This includes the eleven branches of the imperial family that stopped being formerly recognized in October 1947. The same rule does not apply to male members of the family. Women are also not included in the line of succession at all, rather than just bumped down beneath their younger male relatives.

As royal families around the world abandon laws that favor younger sons over older daughters when it comes to succeeding the throne — a law called primogeniture — Japan has held onto their own, which go much further than the laws of many other countries ever have. For example, the United Kingdom abolished primogeniture in 2015, ahead of the birth of Prince George. Before then, a younger brother would usurp his older sister in the line of succession — as Queen Elizabeth‘s daughter Princess Anne was knocked down by her nearly ten years younger brother, Prince Andrew. But females were still included in the line of succession, and if the monarch had no male children (as was the case with Queen Elizabeth’s father, King George VI), then the eldest daughter will inherit throne. Countries such as Sweden, Norway and Belgium got rid of primogeniture even before the United Kingdom did.

But in Japan, even if a girl has no brothers, she still has no a place in the line of succession. Instead, the throne will be passed to the next closest male relative. The country hasn’t always had a strictly-male line of succession and forced women who married outside the family to leave. This is all thanks to a 70-year-plus ordinance called the Imperial Household Law. First introduced in 1947, it limits the line of succession to men, despite the fact that the country has had eight empresses throughout its history. The law also mandates that the royal-born women in the family who marry a person without a noble background must give up their royal status and official place in the family. Even more intensely, the line must only go through imperial-born males. If a woman is allowed to stay in the royal family after marrying a nobleman, her sons still would not be allowed to inherit. Since the law was put in place, eight members of the family have given up their royal status.

As harsh as it may sound, “leaving the family” often means giving up a title and royal status, rather than their familial connections. When the Emperor’s only daughter, Sayako Kuroda, formerly Princess Sayako, left the family in 2005, she was told by her mother “Everything’s going to be OK” and that their family ties would stay. It does mean some serious adjustments lie ahead: Ahead of her own wedding, Sayako took driving lessons and practiced going grocery shopping, according to the BBC.

However, this tightly-regulated succession is creating a predicament for the Japanese imperial family. When Emperor Akihito abdicates the throne, as he’s expected to next year, his son Crown Prince Nahurito will inherit. But Nahurito only has one child, a daughter: Princess Aiko. So when Nahurito dies (or abdicates, though Akihito’s decision to do so is breaking 200 years of precedent), the throne will pass to his younger brother, Prince Fumihito — the father of Princess Mako. Fumihito has a son, Hisahito, who is set to inherit after him, but Hisahito is the only male of his generation in the family.

The imperial family presently has less than 20 members, and experts worry that that number will continue to dwindle as the older generations die off and Akihito’s four grandchildren, three of which are female, marry outside the family. “Under the present system, there is the risk that Hisahito will be the only one left in the imperial family,” Keio University Professor Hidehiko Kasahara told the Express.

There’s been talk of amending the law in the past. In 2011, then-Prime Minister Yoshihiko Noda said he wanted to look at changing the law to allow commoners to remain a part of the family, largely due to the shrinking size of the family as daughters depart when they marry. However, supporters of the law worry doing so will dilute the imperial lineage when a female member of the family has a child with a commoner, according to The Japan Times. That sort of thinking means there’s a definite double standard for women and men in the family: Empress Michiko and Crown Princess Masako were both born into well-to-do commoner families.

The Japanese public wants to see change: A May 2017 poll from Kyodo News reports 62 percent of people support allowing female members to remain a part the imperial family after marrying commoners, and an overwhelming 86 percent would like to see the line of succession include women. However, in a culture and society such as Japan’s, tradition is steep and hard to break, and the talk of changing of the law has never become more than chatter. Current Japanese Prime Minister Shinzo Abe has stayed relatively quiet on the topic, though in 2011, he said such a decision should not be rushed.

“There lies a danger that basic principles that have supported the Imperial household’s long history and tradition through the male lineage may collapse.”