Added to the abdication bill is a resolution that potentially questions whether women who marry outside the family have to rescind their royal rights.

Stepping down for love

Currently, imperial law also decrees that -- unlike in Europe or Great Britain -- any princess who marries a commoner must leave the family.

Mako is one of 14 women in a royal family of only 19 people.

In addition to Princess Mako, there are six other unmarried princesses who could lose their imperial status if they marry commoners, raising the possibility that the royal family will soon not have enough members to carry out its public duties.

Under pressure from the more conservative quarters of his ruling LDP party, Prime Minister Shinzo Abe initially resisted a major push from the opposition to support a draft resolution that would open up discussions on whether female members of the family should be permitted to retain their imperial status after they marry.

Conservatives maintain a change of this ilk could lead to the advent of female succession, unthinkable to some of Japan's traditionalists.

However, in a big concession to the Democratic Party (DP), Prime Minister Abe did allow the additional resolution to be attached to the abdication bill, paving the way for the creation of female-led branches of the family that could potentially take on a share of the royal duties.

Succession crisis

"I think the reason people raise questions as to why women have to leave the royal household when they get married is because Japan is facing a succession crisis," says Jeff Kingston, director of Asian studies at Temple University Japan.

"They have a shortage of male heirs."

Naruhito only has one daughter, Princess Aiko. Next in line to the throne is Naruhito's younger brother, Crown Prince Akishino, followed by Akishino's son, Prince Hisahito, who was born in 2006. His birth put a halt to the renewed debate at the time about the legitimacy of female succession.

Kingston says people are once again beginning to think about the possibility, which would help ease the crisis.

"Opinion polls show the Japanese people are just fine with the idea of having an empress," he says, adding that really it's only conservatives that oppose the idea.

In pre-war days, the emperor was seen as divine, and the idea of a female sitting on the throne is still highly controversial in more traditional circles. However, there have been calls from politicians and academics to review this policy, especially in light of the male heir shortage.

But Japan's ruling Liberal Democratic Party has remained tight-lipped on the issue, firmly ruling out any discussion this time around on constitutional changes regarding the viability of potential empresses.

While Japan might slowly be coming around to the idea of imperial princesses who marry outside the family, after what it believes could be up to 2,600 years of unbroken male rule, it doesn't appear as though there will be a woman on the Chrysanthemum Throne any time soon.