The December 2, 2001 birth of Crown Princess Masako's first child, a baby girl named Aiko, has again brought to the forefront the issue of Japan's Imperial succession.

According to the Imperial Household Law, "the Imperial Throne shall be inherited by a male of patrilineal imperial descent." The exact order laid out in the law, and the current line of succession, is:

  1. the eldest son of the emperor
  2. the eldest son's eldest son
    • none
  3. other sons and grandsons of the eldest son
    • none
  4. the second eldest son and his sons and grandsons
  5. other imperial sons and grandsons
    • none
  6. imperial brothers and their sons and grandsons
  7. imperial uncles and their sons and grandsons.

However, princes Hitachi, Mikasa and their issue are all older than Akishino, making them unlikely to succeed. Since 1965, only female children have been born into the Imperial family, including Princess Nori, the daughter of the reigning Emperor and Empress; Princesses Mako and Kako, the children of Prince Akishino; and now Aiko, the first daughter of the Crown Prince, who would be second in line if the law of succession is changed. In almost ten years of marriage, Crown Princess Masako (37 years old) has given birth once and miscarried once, so having a male heir is starting to appear unlikely.

There is considerable precedent for having a female Emperor (Empress), since no less than eight women have held the throne at one time or another. However, it has been well over one thousand years since the last of real Empress (Shotoku, 764-770), and while records are spotty, it appears that the Empresses were only allowed to reign while male candidates were underage and that they were often mere puppets of the real rulers. Shotoku -- a fervent advocate of Buddhism, who elevated a monk to the post of Chief Minister and seemed intent on making him Emperor -- seems to have been an exception, which may also explain why the practice of allowing females to succeed ended with her. (The sole Empress after Shotoku, Go-Sakuramachi 1762-1771, was just a placeholder until the late emperor's son came of age.)

Japan's political parties, the press and the public seem to support the extension of the right of succession to women nearly unanimously. (The primary exception is the Japanese Communist Party, which opposes the entire institution of having an Emperor.) Opposition to the change seem to come from some of the more extreme nationalist elements and, above all, the sheer inertia of the Imperial Household Agency, which regulates the life of the world's oldest monarchy and is very keen on maintaining traditions. But as the alternative seems to be extinction, I suspect a change in the rules is only a matter of time...

References

thbz's excellent writeup "Emperors of Japan"
http://www.fpcj.jp/e/shiryo/jb/0123.html
http://www.geocities.com/jtaliaferro.geo/relatives.html