From 2001 to 2006, Japan discussed the possibility of changing the laws of succession to the Chrysanthemum Throne, which is currently limited to males in the male line of the Japanese imperial family.
As of October 2026, there are three people in the line of succession to the current emperor Naruhito: Crown Prince Akishino, Prince Hisahito, and Prince Hitachi. Prior to the birth of Prince Hisahito in 2006, the government of Japan considered changes to the Imperial Household Law to allow additional potential successors to the throne. In July 2026, legislation was passed to allow the adoption of former male members in the patrilineal line. Although the adoptee is not eligible to succeed the throne, his male patrilineal descendants are eligible and the order is determined by their natural birth order. Yet, the debate still remains and currently no former male members have been adopted in.
Background
Traditionally, the imperial throne was passed on under custom which resembled the rule of agnatic seniority. Theoretically, the emperor could declare any man or woman his heir, so long as they were of Imperial blood and a member of the Imperial family. A matrilineal emperor was theoretically possible. However, in practice, preference was given to first-born male offspring of a preceding male monarch, followed by his brothers, sons, other males of the immediate male-line family, and ultimately male members of the Shinnōke houses, cadet branches distantly related to the reigning monarch. Because there existed no restrictions on remarriage or polygyny in historical Japan, there existed usually many male relatives who could take over the throne.
However, there have been eight empresses regnant of Japan. All empresses regnant were descendants of the Imperial Dynasty in the male line. Such successions have happened for a variety of reasons. On some occasions, the direct male heir was only a toddler and unable to perform the imperial rituals. In such an instance, his mother, aunt or elder sister, if also of Imperial lineage through her patriline, temporarily took over the throne until the child came to puberty, which was deemed sufficient for a boy's accession. The offspring of female emperors had succession rights under the Nara period law that was used up until the Meiji restoration, and Japan practiced a system of dual lineage, thus most early emperors (Asuka to early Heian period) were related to the Imperial Family via both lines. The last time Japan had an empress regnant was in 1771, when Empress Go-Sakuramachi abdicated in favor of her nephew, Emperor Go-Momozono.
After the Meiji Restoration, Japan imported the Prussian model of imperial succession, in which princesses were explicitly excluded from succession. The Japanese government also banned polygyny, which was previously allowed to any family with noble rank (samurai or kuge), particularly if the first wife could not produce male offspring. The Imperial Household Law of 1947 instituted a further restriction: only the descendants of the male line of Emperor Taishō (the father of then-emperor Hirohito) could be part of the official imperial family and have a claim to succession, excluding all other male lines of the imperial dynasty and specifically barring the emperor and other members of the imperial family from adopting children.
Under Chapter 1: Article 1 of the Imperial Household Law, "The Imperial Throne shall be succeeded to by a male offspring in the male line belonging to the Imperial Lineage".The Imperial House Law of 1947 The line of succession is detailed in Article 2 as:
The eldest son of the emperor The eldest son of the emperor's eldest son Other descendants of the eldest son of the emperor The second son of the emperor and his descendants Other descendants of the emperor Brothers of the emperor and their descendants Uncles of the emperor and their descendants
Situation
The Japanese imperial dynasty, traditionally descended from the Emperor Jimmu, is perhaps the oldest patrilineage in the world, and members of that single dynasty have ruled Japan for nearly 2700 years, according to legends. The ancient Japanese system is of agnatic succession, generally by primogeniture, with the caveat that, in case the imperial family lacked heirs, they may adopt a boy from collateral cadet branches of the Imperial lineage. Four such cadet branches of the imperial family had, from ancient times, held the privilege of supplying an heir in adoption to the throne of Japan. The need for adoption rarely arose, because emperors normally had several consorts, and the sons of all consorts were equally eligible to succeed.
All of these traditions and solutions had been discontinued or prohibited by the 1950s. Emperor Shōwa (Hirohito) was the emperor of the Japanese Empire during World War II. After the war ended, the Diet passed a new Imperial Household Law that limited the succession to agnatic descendants of Emperor Shōwa's father, the Emperor Taishō, thus excluding cadet branches of the imperial family. It also prohibited the practice of adoption. Since the days of the Emperor Meiji, the practice of having several consorts had been discontinued. The imperial family, therefore, became very small after the new Imperial Household Law was adopted.
By the turn of the century, these restrictions had resulted in a situation where the dynasty came perilously close to extinction. Emperor Emeritus Akihito (eldest son of Emperor Shōwa) had only two sons: Naruhito and Fumihito. The younger son, Prince Fumihito, was the first to marry, and he soon became the father of two daughters, then-Princess Mako (b. 1991) and Princess Kako (b. 1994), but he had no son until 6 September 2006, when his wife gave birth to Prince Hisahito. Akihito's eldest son, Naruhito, who married in 1993, did not become a father until 1 December 2001, when his wife gave birth to a daughter, the Princess Aiko. Naruhito and his wife received their child with great joy, since they had almost despaired of parenthood. However, the birth of the princess opened the question of the succession to public debate, because Naruhito's wife, who had suffered a miscarriage previously, and was very close to forty years of age, was unlikely to bear further children.
Akihito's brother, Masahito, Prince Hitachi and his wife have no children.
The two other collateral members of the imperial family also had only daughters: Prince Tomohito of Mikasa had two daughters, Princess Akiko (b. 1981) and Princess Yōko (b. 1983); while Norihito, Prince Takamado had three daughters, Princess Tsuguko (b. 1986), then-Princess Noriko (b. 1988) and then-Princess Ayako (b. 1990). Prior to the birth of Prince Hisahito in 2006, no male heir had been born into the imperial family in nearly 41 years.
Solutions As solutions to this issue, two main logical countermeasures can be considered. In fact, during the mid-Heisei period and later, when the imperial line faced the threat of extinction, both of these proposals were brought to the table for discussion.
Expand the range of candidates while maintaining the principle of patrilineal descent from the first emperor (bansei ikkei). Specifically, this would involve reinstating into the imperial household the male members and male-line descendants of former imperial family branches who lost their imperial status in the past (commonly referred to as the "former imperial family" and their male-line descendants), thereby preserving patrilineal succession (bansei ikkei). Relax the principle from "patrilineal descendants of the first emperor" to simply "descendants of the emperor". In other words, this would entail permitting the inclusion of male members of the general public who are not patrilineal descendants of the first emperor into the imperial family, thereby accepting an unprecedented form of succession not based on patrilineal descent—namely, succession through female or maternal lines (commonly referred to as female-line or maternal emperors).
The two proposals are not simply alternatives, as the first one would seek to reinstate former imperial households, while the latter would seek to allow the female members already in the Imperial Household to succeed to the throne and have children themselves giving the imperial line female line heirs.
Proposals for the return of former princely houses
Historically, male members of collateral branches of the Imperial House who were distantly related to the reigning emperor were at times removed from imperial status through Shinseki kōka (臣籍降下), becoming commoners. Their male-line descendants nevertheless remained part of the broader imperial lineage. In contemporary debates on reform of the Imperial House Law, some commentators and policymakers have proposed restoring descendants of former imperial branches to imperial status in order to address concerns regarding the declining number of eligible heirs to the Chrysanthemum Throne.
Historical precedent exists for the use of collateral branches of the Imperial House to resolve succession shortages. Upon the death of Emperor Go-Momozono in 1779 at the age of 21 years, the throne faced a succession crisis because the emperor left no surviving son, only a daughter, Imperial Princess Yoshiko. To secure the succession, Prince Kanehito of the Kan'in-no-miya house, one of the four shinnōke collateral branches maintained as potential sources of heirs, was adopted by Go-Momozono and subsequently acceded to the throne as Emperor Kōkaku. Historians have regarded this succession as one of the most significant examples of a collateral imperial line being called upon to preserve the continuity of the throne. The accession of Emperor Kōkaku has been regarded as a historical example of a collateral branch of the Imperial House serving as a reserve source of male-line successors to the throne. Emperor Kōkaku's accession in 1779 marked the first succession from a collateral branch of the Imperial House since Emperor Go-Hanazono in the 15th century. Emperor Go-Hanazono himself had been selected from the Fushimi-no-miya branch of the Imperial House after the death of Emperor Shōkō without a surviving heir, demonstrating the historical function of collateral imperial lines in maintaining dynastic continuity.
During the drafting of the Imperial House Law of 1889, Inoue Kowashi argued that, should a succession crisis similar to that associated with Emperor Keitai arise, male-line descendants of earlier imperial branches could be sought even after many generations. According to the records of the deliberations on the Imperial House Law and Imperial Family Ordinance drafts, he maintained that descendants could be recalled even if their separation from the imperial house extended back numerous generations.
Medieval historian Kawachi Yoshisuke has argued, on the basis of his analysis of the Jinnō Shōtōki, that imperial legitimacy was historically understood to derive fundamentally from male-line descent rather than from proximity to the reigning emperor.
Although members of the imperial family have repeatedly undergone shinseki kōka throughout Japanese history, contemporary discussions focus primarily on the eleven collateral princely houses (Ōke) that lost imperial status in October 1947.
All eleven houses were descended from the Fushimi-no-miya line, the oldest hereditary collateral branch established to provide potential successors should the main imperial line fail. Proponents of restoration frequently cite the historical role of the Fushimi-no-miya and its descendant houses as former succession reserves for the throne.
Supporters also note that the Fushimi-no-miya line maintained close ties with the reigning imperial family through adoption and marriage, particularly during the Meiji era and thereafter.