Expected marriage to Kei Komuro would cost Mako her title under law that only applies to female members of monarchy

For Japan’s chrysanthemum throne, the price of falling in love is high if you are female.

News that Princess Mako, eldest grandchild of Emperor Akihito, will surrender her royal status if, as is expected, she marries a commoner, has reignited debate on the male-only succession to the world’s oldest hereditary monarchy.

Under Japan’s controversial law, any female royal family member loses her status on marrying a commoner. The 25-year-old princesses’s impending engagement to law firm worker Kei Komuro, also 25, comes as Japan faces a shrinking imperial family and a possible future shortage of male heirs.



It is currently grappling with the thorny constitutional issue of 83-year-old Akihito’s possible abdication after he hinted last year he feared age could interfere with his duties.



For two centuries, no Japanese emperor has abdicated, and imperial law currently does not allow it. But, while the Japanese parliament is due to consider a draft bill that may allow him to abdicate, and despite there being currently only four heirs, it seems no changes are planned to males only succession.



Princess Mako met Komuro, who once starred in a beach tourism campaign for the city of Fujisawa as “Prince of the Sea”, when they were both studying at the International Christian University in Tokyo. She is the eldest child of Prince Akishino, who is Akihito’s younger son.



Akihito’s elder son and heir, Crown Prince Naruhito, has no sons of his own. Next in line is Akishino, whose 10-year-old son, Prince Hisahito, will follow. Before Hisahito’s birth, in 2006, the possibility of allowing women to ascend the throne was debated, but conservatives argued it would sever what they claim is an unbroken 2,600-year-long line of male succession.



The fourth-in-line is the emperor’s younger brother, Prince Masahito, currently aged 81. Concerns have long been expressed that the succession could be broken if Hisahito does not have a son.



Under the law, Akihito and his two sons were able to marry commoners, who became part of the monarchy.



Princess Mako, however, must leave, as did her aunt, Princess Sayako, the only daughter of Akihito. After Sayako’s low-key 2005 wedding to an urban planner, she moved into a one-bedroom apartment, and learned to how drive and shop in a supermarket for the first time. Her reduced status was, however, compensated for by a payout of more than $1m (£770,000) from the government.

At present there are seven royal family members aged under 30, of whom six, including Mako, are unmarried women who will also lose their royal status if they marry commoners, leaving a much reduced imperial family to carry out public duties.



One solution, which is the subject of intense debate, would be to change the law so women born into the imperial family can continue with their royal duties, thus helping to increase the number of potential male heirs.



The engagement will only become official after a ceremonial exchange of gifts, but is expected to be announced shortly, with a wedding next year, according to public broadcaster NHK.



Questioned by journalists on Wednesday, Komuro dodged the issue of his reported engagement, saying he would only speak about it “when the time comes”.