TOKYO - Japan has opened the possibility of welcoming into the imperial family patrilineal male descendants from former imperial branches through adoption. It is epoch-making and deserves praise.
Past generations have worked to protect the male-line imperial lineage and there is no choice but to preserve it under the given current conditions.
It has been extremely wise that discussions this time have centered on the purpose of ensuring the number of imperial family members as an "urgent" issue, even as a resolution that accompanied a special law on the former Emperor Akihito's abdication called for "measures for stable imperial succession."
As a result, the amended Imperial House Law retained succession by a male offspring in the male line, meaning only men who have an emperor on their father's side can ascend the Chrysanthemum Throne.
It was highly unlikely to see discussions converge if the focus from the outset was only on the adoption of members from former imperial branches to preserve the male line, which supporters of female or female-line emperors would have opposed.
While seeking to maintain the number of both male and female imperial members, meticulous preparations took place so that female-line emperors would not be allowed to reign. At the same time, adoption made it possible to secure men who belong to the imperial lineage, marking a major step toward maintaining the male-line succession.
Crises in direct-line succession have been overcome through collateral relatives and imperial branches. Efforts have also been made to bridge what can be viewed as distance from the throne through marital blood ties.
For example, the 26th Emperor Keitai was separated from the 25th Emperor Buretsu by 10 degrees of kinship and only shared a common ancestor from about 200 years ago. But he married Princess Tashiraka, a sister of Emperor Buretsu, and the 29th Emperor Kinmei was their child.
The former imperial branches that will be eligible for adoption trace a common ancestor with the current imperial family back about 600 years to Prince Sadafusa of the Fushimi branch. Emperor Mutsuhito, posthumously known as Emperor Meiji, married off four princesses to Fushimi-related houses and Emperor Hirohito, posthumously known as Emperor Showa, also married off a princess into the Higashikuni branch, likely reflecting an emphasis on blood ties.
If a female remains in the imperial family after marriage, her spouse and any children born afterward will remain commoners. Although it may be seen natural to make them part of the imperial family, they must remain commoners to avoid having matrilineal imperial family members.
Female imperial members will be registered in the imperial genealogy, while spouses and children will be recorded in Japan's family register system.
Even in cases when Japanese marry foreigners, couples are both listed in the resident registry network despite separate family registers. By also listing the relevant imperial member in the resident registry, family unity is expected to be maintained.
It is very pleasing that Princess Aiko, the only child of Emperor Naruhito and Empress Masako, is active as a female royal and enjoys strong public popularity. But succession is a separate issue. Under the current legal system, "Emperor Aiko" is impossible.
At Ceremonies for the Proclamation of Crown Prince, the emperor declared at home and abroad that his younger brother, Crown Prince Fumihito, is first in line as heir.
Article 1 of the Constitution of Japan states that the emperor's position derives from the "will of the people" but that is different from "public opinion." It is unthinkable to allow Princess Aiko to become a reigning empress amid the shifting public sentiment.
Having the throne passed down through the male line is an imperial tradition, and the male line guarantees the emperor's legitimacy. While Princess Aiko is a male-line female and theoretically may become an heir, there is no need to consider a female emperor because there are already three male-line male heirs with succession eligibility.
Akira Momochi, born in 1946 in Shizuoka Prefecture, is a professor emeritus at Kokushikan University. He completed graduate studies at Kyoto University and specializes in constitutional law and research on the imperial system. He has also served as professor emeritus at Nihon University since 2017. His books include "Q&A on the Imperial Succession Issue."
