Succession

Historically, the succession to Japan's Chrysanthemum Throne has generally passed to male descendants in the imperial lineage. In part, the Japanese imperial dynasty owes its longevity to the use of concubines, a practice that only ended in the Taishõ period (1912-1926). The Japanese monarchy also relied on the specially designated collateral lines or shinnõke (shinnõ houses).

If the imperial household failed to produce an heir, one of the shinnõke could provide the future emperor. There were four such collateral lines in the Edo period: Fushimi, Katsura, Arisugawa, and Kan'in. Emperor Kõkaku (reigned 1780-1817), the lineal descendant of all subsequent emperors, was a scion of the Kan'in house. The Katsura and Arisugawa houses died out in 1881 and 1913, respectively. A scion of the Fushimi house succeeded to the Kan'in house in 1884. The Fushimi house was the progenitor of nine other cadet branches (õke) of the imperial family during the Meiji period. It and its offshoots were reduced to commoner status in 1947.

Before the Meiji Restoration, Japan had eight female tennõ or reigning empresses. Imperial daughters and granddaughters, however, only ascended the throne as a "stop gap" measure. Each abdicated once a suitable male descendant in the male line of imperial descendants became available. Three empresses regnant, Suiko, Kõgyoku, and Jitõ, were widows of deceased emperors and princesses of the blood royal in their own right. One, Gemmei, was the wife of a crown prince and a princess of the blood royal. The other four, Genshõ, Kõken (Shõtoku), Meishõ and Go-Sakuramachi, were the unwed daughters of previous emperors. None of theses empresses gave birth or married after ascending the throne.

Article 2 of the 1889 Meiji Constitution (or Constitution of the Empire of Japan) stated, "The Imperial Throne shall be succeeded to by Imperial male descendants, according to the provisions of the Imperial House Law." The 1889 Imperial Household Law fixed the succession on male descendants of the imperial line, and specifically excluded female descendants from the succession. In the event of a complete failure of the main line, the throne would pass to the nearest collateral branch, again in the male line. If the empress did not give birth to an heir, the emperor could take a concubine, and the son he had by that concubine would be recognized as heir to the throne. This law, which was promulgated on the same day as the Meiji Constitution, enjoyed co-equal status with that constitution.

Article 2 of the Constitution of Japan provides that "The Imperial Throne shall be dynastic and succeeded to in accordance with the Imperial Household Law passed by the Diet." The Imperial Household Law of 16 January 1947, enacted by the ninety-second and last session of the Imperial Diet, retained the exclusion on female dynasts found in the 1889 law. The government of Prime Minister Yoshida Shigeru hastily cobbled together the legislation to bring the Imperial Household in compliance with the American-written Constitution of Japan that went into effect in May 1947. In an effort to control the size of the imperial family, the law stipulates that only legitimate male descendants in the male line can be dynasts; that imperial princesses and princess lose their status as imperial family members if they marry outside the imperial family; and that the Emperor and other members of the imperial family may not adopt children.

There is a potential succession crisis since no male child has been born into the imperial family since Prince Akishino in 1965. Following the birth of Princess Aiko, there was some public debate about amending the Imperial Household Law to allow women to succeed to the throne. In January 2005 Prime Minister Koizumi Junichiro appointed a special panel comprised of judges, university professors, and civil servants to study changes to the Imperial Household Law and to make recommendations to the government. One of the options under consideration would be to allow females in the male line of imperial descent to succeed to the throne.