Japan’s parliament enacted a historic revision to the Imperial House Law on Friday, introducing mechanisms to bolster the dwindling number of royal family members while reaffirming the prohibition on female succession. The legislation, passed by the upper house with support from the ruling Liberal Democratic Party, its coalition partner Komeito, and several opposition groups, permits the imperial family to adopt unmarried male descendants over the age of 15 from eleven former branch families stripped of their status after the Second World War. It also allows female members to retain their imperial titles and official duties after marrying commoners, a right previously reserved for men. The changes will take effect three months after promulgation, with a mandated review every thirty years.

Viewed from within Japan’s political establishment, the revision is framed as an urgent measure to prevent the extinction of the world’s oldest continuous hereditary monarchy. The imperial family now comprises only sixteen members, five of whom are men, and the line of succession rests precariously on 19-year-old Prince Hisahito, the sole male heir of his generation. Government officials, including Chief Cabinet Secretary Minoru Kihara, argued that adopted males and their male-line descendants would become eligible for the throne, securing the dynasty’s future. Prime Minister Sanae Takaichi and conservative lawmakers have consistently defended male-only succession as essential to imperial legitimacy, a principle they describe as rooted in an unbroken paternal lineage stretching back over two millennia.

Opposition parties, constitutional scholars, and a significant majority of the Japanese public have challenged this reasoning. The Constitutional Democratic Party, the Japanese Communist Party, and Reiwa Shinsengumi voted against the bill, warning that the adoption mechanism is impractical and that the exclusion of women from the throne entrenches gender discrimination. Legal experts who testified before the Diet described the legislation as unconstitutional, while former imperial family member Asahiro Kuni publicly stated he would advise his grandchildren to refuse adoption, citing the difficulty of adapting to palace life after growing up “breathing the air of freedom.” Opinion polls conducted by Asahi Shimbun and Kyodo News show that between 72 and 83 percent of respondents favour allowing a female emperor, a position also urged repeatedly by the United Nations Committee on the Elimination of Discrimination against Women. Japanese authorities have dismissed such external recommendations as inappropriate interference in a fundamental state matter.

The imperial succession debate unfolded alongside the passage of two other notable bills. A new law criminalises the public desecration of the national flag in a manner causing “extreme discomfort or disgust,” with penalties of up to two years in prison, a move critics say lacks the clarity required for criminal statutes and could chill political expression. A separate revision to plant variety protection laws extends breeders’ rights and enables injunctions against unauthorised overseas sales of Japanese-developed fruits, responding to estimated annual royalty losses of nearly 20 billion yen from varieties like the Shine Muscat grape. The imperial house revision, however, remains the most consequential, with its long-term viability questioned by analysts in Tokyo and London who note that the adoption provision may fail to attract candidates, leaving the dynasty’s fate tied to the marriage and offspring of a single teenager. The law’s supplementary resolution calls for consideration of the environment surrounding adopted members, but the fundamental dispute over female succession is expected to resurface well before the first scheduled review.