The one-off legislation paving the way for the abdication of Emperor Akihito as early as next year, enacted last week with near-unanimous support in the Diet, was a product of political compromise that either bypassed or left blurred various issues surrounding the Imperial family, which will likely come back in the not so distant future. It addressed the 83-year-old Emperor's wish to retire due to concern that his advancing age and frail health will prevent him from performing his duties — sentiments that he expressed in a video message last August — but it failed to provide answers to the questions that could stand in the way of his other wish in the message — that "the duties of the Emperor as the symbol of the State can continue steadily without a break."

The Imperial House Law stipulates that an emperor will be succeeded by a male heir upon his death, and does not provide for Imperial abdication, which was common in pre-modern eras. Without amending the principles of the law, the administration of Prime Minister Shinzo Abe readied special legislation applicable only to Emperor Akihito, whose expected abdication around the end of 2018 will be the first in some 200 years. Although the government indicated that the legislation "can serve as a precedent" for future Imperial abdication, the succession rule under the Imperial House Law was kept intact. Crown Prince Naruhito, who will take over from his father, will have turned 58 when he ascends the throne — even older than when Emperor Akihito did so at the age of 55 in 1989. Abdication for similar reasons will not be an issue limited to the current monarch.

Public discussions over Emperor Akihito's abdication shed light on questions over sustainability of Imperial succession under the male-only, paternal-lineage-only rule. Of the 18 Imperial family members supporting the Emperor, only four are males in line to the throne. When the Crown Prince takes the throne, his brother Prince Akishino, now 51, will be the next in line, and the only younger-generation male in the family is Prince Akishino's 10-year-old son, Prince Hisahito. Under the Imperial House Law, female members lose their Imperial status when they marry a commoner. Just as the abdication bill was being prepared, news broke that Princess Mako, the eldest daughter of Prince Akishino, would soon be engaged to a former university classmate. Like the nation's population as a whole, the Imperial family is rapidly aging and shrinking, and the succession rules are accelerating the process.