Japanese succession controversy

The Japanese succession controversy refers to desires to change the laws of succession to the Japanese Throne, which is currently limited to males of the Japanese Imperial Family.

Traditionally, the imperial throne was passed on under custom which resembled the rule of agnatic seniority. Theoretically, any male or female with patrilineal lineage to early Japanese monarchs, who descended in direct male line from the first emperor, Jimmu, could come to hold the Chrysanthemum throne. In practice, preference was given to first-born male offspring of a preceding male monarch, followed by his brothers, sons and other males of the immediate male-line family; and ultimately followed by representatives of Shinnoke houses, in other words, male-line relatives, occasionally very distant male cousins.

Because there existed no restrictions on remarriage or polygyny in historical Japan, there existed usually a plenitude of male relatives who could take over the throne. However, there are several historical instances of women holding the throne. An empress's offspring does not have claim to the throne from the said maternal lineage, so assigning a female to the throne had the convenient effect of postponing succession disputes.

On other occasions, the direct male heir was yet a toddler and unable to perform imperial rituals. In such instance, his mother, aunt or elder sister, if also held 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.

After the Meiji Restoration, Japan imported the Prussian model of imperial succession, in which princesses were explicitly excluded from succession. More significantly, as a part of the effort to westernise and modernise Japan, the Japanese government banned polygamy, which was previously allowed to any family with noble rank (samurai or kuge), particularly if the first wife could not produce male offspring. After World War II, a further restriction was instituted. New rules meant that only the closest relatives of the then emperor Hirohito (children and descendants, siblings and their descendants) could be part of the official Imperial family, and have a claim to succession.

...
Wikipedia