With the abdication of Emperor Akihito and the enthronement of his son, Crown Prince Naruhito, there will be only three Imperial family members in line to the throne — who under the Imperial House Law must be males born to the paternal line of the family: Prince Akishino, 53, who will become the Crown Prince and first in line; his 12-year-old son, Prince Hisahito; and Prince Hitachi, the 83-year-old brother of the retiring Emperor.
Given that Prince Hisahito is the family's sole male member of his generation, it seems inevitable that stable Imperial succession will be threatened at some point as long as the male-only succession rule established during the Meiji Era is kept intact. The coming transition from Heisei to the new era of Reiwa should provide a chance to kick off political discussions on what needs to be done to avert a crisis to the future of the Imperial family system.
The thinning ranks of the Imperial family, in particular the declining number of males in line to the throne, has long been deemed a looming problem. When the Heisei Era began in 1989, Prince Akishino was at that point the last male born to the family — in 1965. In 2005, an advisory panel to Prime Minister Junichiro Koizumi compiled a report recommending changes to the succession rules to ensure stability in the Imperial succession. The measures included allowing an empress to reign and maternal line succession, and that the first-born child, whether male or female, should take precedence in the order of succession. These proposals were apparently developed with Princess Aiko, born in 2001 to the Crown Prince and Crown Princess, in mind.