Did You Know
When the Japanese emperor's granddaughter marries law firm employee Kei Komuro next year, her life will undergo a dramatic change.
Princess Mako, 25, will lose her title and leave the cloistered imperial household to live with her husband in the outside world.
She will receive a one-off payment, after which the couple will be expected to provide for themselves. She will vote and pay tax, shop and do her own chores. If the couple have children, they will not be royal.
But her departure means one fewer to carry out official duties. It is also reigniting debate about the shrinking monarchy, the role women play in it and future succession.
Emperor Akihito, 83, has already indicated that he wants to step down. As the female royals get married, the monarchy is expected to contract further.
There is only one boy among the younger royals, 10-year-old Prince Hisahito. If nothing changes, the future of the imperial institution will rest solely with him.
"If you think about it there is a possibility that all but Prince Hisahito will leave the royal household in 10 to 15 years time," said Isao Tokoro, professor emeritus at Kyoto Sangyo University.
"I think it [the engagement] gave us an opportunity to think about the problem. The system should be reformed urgently so we don't lose more members from the Imperial family."
'Cheerful home'Under Japan's Imperial Household Law of 1947, princesses who marry commoners are removed from the royal family.
That same law slashed the number of Japanese royals, removing 11 out of 12 branches of the imperial family as a cost-cutting measure. That means there are no royal males for current princesses to marry.