Japan Enshrines Male-Only Imperial Succession, Ruling Out Princess Aiko

Japan’s parliament has enacted a revision to the 19th-century Imperial House Law that formally restricts the throne to men of paternal lineage, ruling out Emperor Naruhito’s only child. Supporters call it a defence of an unbroken bloodline; critics warn it may hasten the decline of a monarchy already running short of heirs.

What does the revision change?

The law contains two main measures. The more contested allows unmarried male descendants of distant imperial relatives, aged 15 or over and of paternal lineage only, to be adopted into the royal family so they can father future heirs.

The second allows princesses to retain their royal status and continue official duties after marrying commoners, which the current law does not permit.

Neither measure alters the core rule. Only boys born to men with royal blood may inherit, although an emperor’s mother may be a commoner, as is the case with the present emperor.

The adoption provision draws on history. In 1947, 51 members from 11 branch families gave up their royal status, largely to ease the financial burden on the monarchy after the war. Their male descendants are the pool the new law is designed to draw from, though no candidates have been publicly identified and it is not clear how many would accept.

Who is affected?

Princess Aiko, Naruhito’s 24-year-old daughter, is barred from the throne because she is a woman. She is widely popular in Japan, and on public engagements the crowds calling her name have at times drowned out those greeting her parents.

The succession instead passes to the emperor’s younger brother, Crown Prince Akishino, who at 60 is only six years younger than Naruhito and has reportedly indicated he would be too old to serve. After him comes Akishino’s 19-year-old son, Prince Hisahito, then Naruhito’s 90-year-old uncle, Prince Hitachi.

The arithmetic is stark. Of the 16 adults in the imperial family, only five are men, and there are no children. Hisahito was the first boy born into the family in four decades.

What is the argument for it?

Prime Minister Sanae Takaichi, Japan’s first woman prime minister, said she was deeply moved by the enactment. She and other conservatives hold that the male bloodline is the sole source of the emperor’s authority and legitimacy.

Takaichi has pointed to a 2021 expert panel that concluded eligibility should be limited to male-line male descendants, and said the government respects that finding.

What do critics say?

Hideya Kawanishi, a monarchy expert at Nagoya University, described the measure as an effort to rule out female monarchs and protect the male line at any cost. “They cannot say it’s male chauvinism, so they call it tradition,” he said.

Royal watchers warn the revision could imperil an institution that traces its line back roughly 1,500 years, by narrowing the pool of eligible heirs at precisely the moment it is shrinking fastest.

Public opinion has long pointed the other way. A Yomiuri Shimbun poll conducted in late 2018 found nearly two-thirds of respondents favoured revising the law to allow a woman to inherit. That gap between public sentiment and legislative outcome is now written into statute.

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