AUDIE CORNISH, HOST:

A Japanese princess is getting engaged. While that's cause for celebration in the country, it's also reviving a debate about the rigid law that governs Japan's monarchy. Women cannot inherit the throne, and unless they marry royalty neither can their children. That means the royal family will continue to shrink. Earlier I spoke with Motoko Rich, New York Times' Tokyo bureau chief. First I asked her to explain Japan's law.

MOTOKO RICH: It's all male, male, male. So the first thing is that the current law, which dates back to the 19th century, only men can rule from the throne. And the second part of the law is that say an emperor has several children, some of whom are men and some of whom are women. Only the men can pass down the royal genes, as it were. So if an emperor has daughters who then go on to have sons, those sons are not eligible to reign on the throne.

CORNISH: So help us understand the context, then, for the princess' situation. She's going to marry a college boyfriend, essentially - right? - someone she met at university.

RICH: Right. This is Princess Mako. She's 25 years old. And she met her boyfriend Kei Komuro in 2012. And when she marries him, because he's not a member of the royal family, she will have to leave the family. That is the rule. He does not get to become a prince and she will become a commoner.

CORNISH: Now, how has this sparked some debate in Japan? Like, do people in the public think, hey, maybe we need to change the laws?

RICH: Absolutely. When you look at polls, about 86 percent of the Japanese public say it's time to allow women to ascend to the throne, and about two-thirds of them say it's time to allow the royal lineage to pass either through men or women. The other reason that this is on the table at the moment is because the current emperor, who's 83 - this is Emperor Akihito - is very old and tired. And he wants basically to retire, or in his case it would mean he has to abdicate. And no Japanese emperor has abdicated in 200 years.

So the government - Prime Minister Shinzo Abe is proposing a kind of one-time carve-out for this empire. They're going to let him abdicate, but they will not permanently change the law for anyone else who comes after. The reason why this has come up is because in talking about the one-time carve-out there was a debate about whether they should overhaul the law altogether.

And one of the questions that would have come up if they were to do that is whether we should also open the door for women to become rulers on the throne. And the very conservative wing of the Liberal Democratic Party said absolutely no way.

CORNISH: But it sounds like a change for women in imperial law could have some symbolic meaning for the rest of the economy, for the culture.

RICH: Absolutely. I mean, because the emperor is so revered, if the law were changed to allow women to ascend to the throne I think that would be very important as a kind of inspiration and role model for the women in the country that feel that they aren't yet accorded equal rights to men.

CORNISH: Motoko Rich, in the meantime, what happens to this royal family I guess after this chapter, right? Are there enough males in the family to keep the monarchy going if the law stays the same?

RICH: No. That's the other very interesting point here is there are only a total of 18 members left in the imperial household. And there are only five males, including the current emperor and his two sons, his brother and his grandson, who's now 10 years old and is, in fact, the younger brother of Princess Mako, the woman who just got engaged. So there just aren't that many of them left. And it puts an enormous amount of pressure on this little boy, this 10-year-old boy, that when he comes of age there's going to be pressure on him A, to marry and B, to produce a male heir.

CORNISH: All right, well, we'll give him some time (laughter).

RICH: Exactly (laughter).

CORNISH: Motoko Rich is the Tokyo bureau chief for The New York Times. Thank you so much for explaining it to us.

RICH: Thanks so much for having me. Transcript provided by NPR, Copyright NPR.