Affiliation thresholds, 530 to present

The evolution of rules for belonging in Japan

By William Wetherall

First posted 10 April 2009
Last updated 20 July 2009

Pre-Meiji affiliation Early population registers | Peerages (Shinsen shojiroku) | Temple registers (Shumon aratame cho)
Interstatus marriage 530 Status of karako | 645 Law of men and women | 789 Notice on good-base intermarriage
Nationality Proto "nationality" | "Nationality" before 1899 | Nationality since 1899-2009
Thresholds of affiliation in Japan, 530 to present (Table)

This article examines how status conventions in early Yamato and Japan established the foundations of family law which inspired the affiliation rules that came to be encoded in Meiji and subsequent versions of the Family Register Law, the Civil Code, and the Nationality Law.

Pre-Meiji affiliation



Early population registers



Peerages (Shinsen shojiroku)



Temple registers (Shumon aratame cho)



Interstatus marriage

Early Japanese chronologies contain a number of reports concerning unions of, or offspring born between, people affiliated with different territories or polities, different clans or families, and different social classes or castes. Rules governing the statuses of the couple and their offspring appear to have varied from place to place and period to period, but it is possible to make some generalizations about the direction in which the rules have changed over the centuries.

The different affiliations of a Yamato man and a Kara woman appear to have affected the status of a child born in Kara (Korea) between such a couple. The offspring of unions between persons of different status in Yamato (Japan), such as "good people" and "slaves", appear to have been similar.


530 report on status of Karako child


See 530 Status of child born in Mimana (Imna) to Kara wife of Yamato man for the text and two translations of this account.


645 Law of men and women

Marriage between so-called "good people" and "slaves" was not prohibited in the Taika reforms of circa 645. In effect, however, laws determining the status of children implied that such interstatus unions were not acceptable. And at least one article in the Yōryō code, as related in Ryō no gige, implied that the five colors of base people were expected to marry their own kind.

The affiliation was patrilineal for children born between two good parents or between a good woman and a slave man, and were matrilineal for children born between a good man and slave woman or between two slaves. In other words, all children became slaves unless both parents were good.

Had marriages been equally divided between the four possible mixtures of status of parents, then three out of four children would have become slaves. More striking, though, is that while the children of slave women would always belong to their mothers regardless of their father's status, the children of good women never belonged to their mothers.

The status standards prescribed in the 645 Law of men and women (男女法 Danjohō), as reported in the Nihon shoki (721), imply a one-drop rule, according to which the "good" world remains pure while the "slave" world absorbs all hybrids.

See 645 Status of children of "good" and "slave" men and women for the text and two translations of this decree.


F = father
M = mother
G = good
s = slave

F+M   Child's affiliation

G+G = GG patrilineal = G = pure G
G+s = Gs matrilineal = S = hybrids absorbed by S 
s+G = sG patrilineal = S = hybrids absorbed by S
s+s = ss matrilineal = S = pure S within S

Take two pure populations, one "good" and the other "slave", and let them freely mix under the above essentially Mendelian rules. Over the span of several generations, the "slave" population will increase at the expense of the "good" population. Moreover, the "slave" population as defined will become increasingly mixed at the expense of both the "good" population (which is pure by definition) and the pure "slave" population.

The decline in relative size of the "good" population will have a negative impact on revenues in a system that taxes only "good" people. Unless "good-slave mixed marriages" can be discouraged, the only solutions are to change the tax system or the classification system.

Japan, between the late 8th and early 10th centuries -- essentially during the Heian period -- chose the option of changing the classification system toward one which liberated first the children, then the parents themselves, from the onus of the good/slave distinction. And the social history of the following millennium -- essentially down to the present century -- has been one of diminishing varieties of legally defined classes and castes.


789 Notice on good-base intermarriage

A 789 notice in the Shoku Nihongi states that children born to slave women who had married good men, or to good women who had become wives of slave men, were thereafter to listen to and abide with good people (自今以後。婢之通良。良之嫁奴。所生之子。並聴従良。SN 40, Kanmu, Enrakyu 8-5-18, 789-6-19 [15], SZKT SN 2:536).

The notice began with with the observation that "good-base intermarriage" (良賤通婚) was clearly prohibited by codes. Yet men and women under heaven were wantonly mixing together. The high were fornicating with the low. Some public affiliates [the good people of the sovereign's dominion] were changing into and making slaves (公民之後変作奴婢). Apparently there was no way to reform such bad practices. So all offspring of mixed good-base alliances were to be regarded as good. Which meant they would count as taxable heads.

To what extent people took class and caste distinctions seriously is not clear. The warps and woofs of the 645 and 646 decrees and later codes were heavily Chinese. The more plastic aspects of government were being forced in a Chinese mold, but many Yamato customs, which considerably varied regionally, did not easily if at all yield to new rules imposed by way of emulating Chinese political civlization.

There is plenty of evidence that the "five color" distinctions among so-called "base" people were ever as hard and fast as might seem from a reading of the law. Apparently the distinctions did not stop people from mixing their colors, as it were.

The mid 7th-century criteria for classifying children formally lasted only 150 years. the 789 notice is but one example of how the ritsuryō system of law was beginning to crumble. A century later, the highly Sinified "slave" (奴婢 nuhi) classification had fallen into such disuse or abuse that, in 907, it was simply abolished. Some historians date its demise to the last decade of the previous (i.e., 9th) century.





Proto "nationality"

A 530 account in Nihon shoki reports that two Karako sons of Kibi were killed by another Yamato official in Mimana (Imna). An interlineal comment explains that "[A child] born to a barabaria woman a Great Yamato person has taken as his wife, shall be a Kara child."

Compare this statement with the second provision in the 645 "Law of men and women".

530 explanation

[A child] born to a barabaria woman a Great Yamato person has taken as his wife, shall be a Kara child.

645 provision

Should a child be born to a slave woman a good man has taken as his wife], allocate [the child] to its mother.

Japan did not become a nation until 1868, and did not define its nationality until 1899. Suppose, however, that when Kibi's children were born, there had been a Yamato nation, peopled by Yamato nationals, whose nationality was determined by a hypothetical "nationality law" in 530. And say this law differentiated between "Yamato" and "non-Yamato" in the same way that the 645 decree differentiated between "good" men and women and "slave" men and women.

Such a law would have deemed that only a child born to a Yamato man and woman would be a "Yamatoko" and as such would be affiliated with the father. Children born between a Yamato man and, say, a Kara woman, would have been regarded as its mother's child, hence a Karako.

Unfortunately we have no reports of a Yamato woman becoming the wife of a Kara man, much less how children from such an alliance would have been classified. The hypothetical "nationality law" would have stipulated that non-Yamato people became Yamatoites when they migrated to Yamato and enrolled in Yamato registers.

Some newbie Yamatoites would have been classified as "good" or "slave" men or women depending on their recognized social standing. Regardless of their non-Yamato origins, they would not have been treated differently from other Yamatoites of comparable class or caste.

Takano no Asomi Niigasa, a consort and later wife of Kōnin, was a daughter of Yamato no Fumibito Ototsugu, who traced his descent to Prince Sunta, a son of the Paekche king Muryŏng. But she, like her father, would have been considered of Yamato nationality. Her son, Prince Yamabe, succeeded his father as Kanmu. She was initially one of Kōnin's consorts (側妾 sobameshi). Later, as Prince Yamabe's birth mother, she became a grand consort (大夫人 daifunin). Her second son was Prince Sawara.

The hypothetical 5th century Yamato nationality law would look like this compared with Japan's 1899 and the 1985 revision to the 1950 law (which was essentially like the 1899 law).

Hypothetically, Yamato laws recogined only marriages between Yamato nationals. They also subordinated females to males in matters of marriage and family. Accordingly, only children born between Yamato parents would acquire Yamato nationality, and such a child would be affiliated with its father and its father's family. Under such a system, no child born between a Yamato subject and an alien would qualify for Yamato nationality.

However, there is no evidence that marriages between Yamato and alien subjects were not recognized. Nor is there any evidence that children of married parents belonged more to their fathers than their mothers.


"Nationality" before 1899



Nationality laws since 1899



Thresholds of affiliation in Japan, 530 to present

Thresholds of affiliation in Japan, 530 to present

From the earliest historical times, subjecthood first in Yamato and later in Japan has been based primarily on territorial affiliation facilitated by household registration and provisions for change of allegiance. Affiliation at time of birth has mainly been through descent from a registered parent. Over the centuries, the threshold for affiliation at time of birth has fallen as the legal status of mothers has approached and even exceeded that of men in family law.

Until 1985, the rules for affiliation through descent were primarily patrilineal and secondarily matrilineal. In 1985, not only did they become ambilineal, meaning affiliation if either parent is Japanese, but matrilineality is now a more certain cause of affiliation than patrilineality.


J = Japanese
a = alien

F + M = C > S

F   father
+   alliance
M   mother
=   issue 
C   child
>   becomes
S   status


Affiliation = Status under Yamato or Japanese conventions or laws

1873 "Japanese" (Nihonjin) used in 1873 proclamation
      "national" (kokumin) also often used
       = affiliation with nation [Japan]

1890 "subject" (shinmin) used in 1890 Constitution
      = affiliation with sovereign [emperor]
      "national" (kokumin) continues to be used

1899 "Japanese" (Nihonjin) used in 1899 Nationality Law
      Neither "subject" nor "national" used in law
      Formal beginning of "nationality" (kokuseki)
      Formal beginning of "naturalization" (kika)

1945 "shinmin" not used by Hirohito after
      Empire of Japan surrendered to Allied Powers
      since acceptance of the terms of surrender
      implied that nationals were no longer subjects

1947 "national" (kokumin) used in 1947 Constitution

1950 "national" (kokumin) used in 1950 Nationality Law
     "Japanese" (Nihonjin) no longer used in laws

Status acquired through birth or at time of birth

Early customs and codes Nationality laws
530 and 645 17th century 1899-1950 1950-1984 1985-2008 2009-2040
Jus sanguinis    Right of blood, Family lineage
J+J = JJ > J J+J = JJ > J
a+J = aJ > a a+J = aJ
> J > a > J
Status of mothers, hence of children, changed from "J" to "a" to "J"
a+J = aJ > J
Unmarried (father unknown)
Married (father stateless)
a+J = aJ > J
Married or unmarried
(father's status irrelevant)

The Nationality Law was primarily patrilineal until 1985 when it became ambilineal.
a+J = aJ > a
Married (father not stateless)
J+a = Ja > a J+a = Ja > J ?
Probably became Japanese but examples only in fiction
(e.g. 鷹ノ羽の城、白石一郎、1981)
J+a = Ja > J
Nationality Law provisions for acknowledgement BEFORE birth
J+a = Ja > J
None but
J+a = Ja > J
None but
J+a = Ja > J
a+J = aJ > J
None but implied
Nationality provisions for acknowledgement AFTER birth
J+a = Ja > J
a+J = aJ > J
No provisions
for post-birth
J+a = Ja > J
a+J = aJ > J
If married
J+a = Ja > J
a+J = aJ > J
J+a = Ja > a ?
No examples
even in fiction.
J+a = Ja > a
Unmarried &
J+a = Ja > a
Unmarried &
J+a = Ja > a
Unmarried &
J+a = Ja > a

Lineal descent and parental ties

The above ordering of alliances suggests that, whereas in the past there were times when status as a Japanese person, subject, or national was more readily acquired fathers than mothers, today fathers are legally inferior to mothers with regard to the acquisition of Japanese status through lineal descent. However, surrogacy birth has made parental ties as difficult to establish for women as for men.

Paternal acknowledgement

Recognition of a child before or at time of birth has generally been by the father, since the woman who gives birth is taken to be the mother. If the woman is married, the father is taken to be her husband, unless she had remarried within a stipulated period after divorcing another man.

Maternal acknowledgement

Acknowledgement by the mother is conceivable, though. And except for the period 1950-1984, Japan's Nationality Law has provided for both paternal and maternal acknowledgement after birth. Family law does not as yet provide, however, for maternal acknowledgement of a child that has issued from the womb of another woman.

Jus soli    Right of soil, Place of birth
?+? = ?? > a ? J ?
No examples are known. However, a foundling who was thought to be the child of an alien would probably have been registered as the child of its adoptive parents and treated accordingly.
?+? = ?? > J
When both parents are unknown. A foundling infant will be treated as Japanese so long as neither of its parents is known, but as an alien if only one parent is known and is an alien, and could become stateless.
a+a = aa > a
Statelessness would not have been a possible status since there was no nationality. Children of known parents would have been treated like their parents.
a+a = aa > J
When both alien parents are stateless. If only one is stateless, the child will be treated as an alien, and will become stateless if unable to acquire a nationality.

Status acquired through legal agency later in life

Early customs and codes Nationality laws
540 and 645 17th century 1899-1950 1950-2040

a    >   J
Allegiance change
Territorial affiliation gained through submission and pledge of allegiance to territorial authority. Acquired by enrollment in registers in locality under authority's control.

a    >   J
Nationality gained through permission of Minister of Justice. Acquired by registration after qualification and approval of petition to change allegiance.

a    >   J
Affiliation derived through family ties
Affiliation with a territory gained through marriage to or adoption by an affiliate of the territory, following customary family law.
William Adams acquired status through samurai enfranchisement as Miura Anjin (1564-1620) if not through his marriage.
Lafcadio Hearn acquired the status of being Japanese as Koizumi Yakumo (1850-1904) through a husband adoption provision in a 1873 odinance.

a    >   J
Derived nationality
Aliens gained Japanese nationality through marriage to or adoption by a Japanese national, based on automatic operation of laws upon submitting notifications and related documents.

a    <>   a
Derived nationality no longer possible, reflecting changes in international conventions, which no longer subscribe to the principle that family members -- spouses and their children -- should have the same nationality.


The end of derivative nationality from 1950 struck the biggest blow to Japanese parents who would adopt an alien child or adult. Child and adult adoptions remained possible between Japanese families, but the adoptees were already Japanese. And Japanese could adopt alien children, but the children had to be naturalized if the parents wanted them to be Japanese.

The Nationality Law rests on a foundation of family law. And under the 1899 Nationality Law, is was possible for Nishiyama Sen (1911-2007), best remembered as a simultaneous interpretor, to become Japanese through adoption as an adult by his own Japanese mother. Born an American, and entirely raised and educated in the United States, Nishiyama came to Japan in the 1930s with a master's degree in electrical engineering, but found that he needed to be a Japanese national in order to get a government-related job in electronics.

Japanese adoption laws have somewhat changed. Today they permit the adoption of practically anyone who is not an older person, an ascendant, or one's own wedlock child. Thus one can adopt one's own out-of-wedlock biological child, or a biological younger sibling or grandchild, or someone who is not biologically related, inclduing an adult if Japanese, or an alien if a minor.

The problem is that the Nationality Law no longer provides for a child to acquire nationality derivatively through an adoptive relationship with a Japanese national. A family may even adopt its own biological child, born to an alien surrogate mother, but the child will have to be naturalized in order to become Japanese.

None of this speculation should be taken as historical fact. Nothing certain can be construed from the interlineal comments on the 530 and 541 notices in the Nihon shoki -- completed in 720, two centuries later -- long enough for trivial details like why Kibi's kids were called "Karako" had been lost or forgotten. It is not even clear when the comments were written. Some may have added much later by copiests, but a few may have been part of the original compilation.

Nihon shoki was compiled barely half a century after the 645 law of men and women decree, the account of which is probably based on contemporary primary documents -- unlike the 530 and 541 accounts of Kibi and Nasochi. The chronology was completed only two years after the completion of the Yōrō code, which marked the height of attempts to introduce Tang-style laws in what by then was called Nihon.

Early marriage laws

Several articles in Ordinance 8 (Households) of Ryō no gige pertain to marriage. Article 24 allows males to marriage at age 15 while females can marry at age 13, but Article 24 requires a woman to have the permission of her family. Article 27 calls for dissolution of an alliance should a man take [a woman] as his [approved] wife or mistress after committing an indiscretion [with her], even when their meeting [union] [beforehand] has been pardoned [by approving relatives] (凡先奸 [姧] 後娶為妻妾。雖会赦猶離之。SZKT RG:103-104).

Ryō no gige 8-35

Article 35 of Ordinance 8 (Households) of Ryō no gige makes this provision for marriage between the "five colors" of "base people" (賎民 senmin) (structural translation mine).

令義解、8 戸令、35 当色為婚条

Kanbun 凡陵戸。官戸。家人。公私奴婢。皆当色為婚。(SZKT RG:103-104)

Japanese translation   陵戸、官戸、家人、公私の奴婢(公奴婢・私奴婢)は、皆、同種同身分間で婚姻すること。

Structural translation   Tomb households [tomb keepers]. Official households [servants of court or ministries]. House people [clan, family servants]. Public [government] and private [male and female] slaves. All are to marry a [person of] corresponding color [like status].

Sansom's translation (Sansom 1934:145)

35. Tomb serfs and public serfs, servants, public and private slaves may marry only in their own category.

Sansom comments at considerable length on what he calls the "free people" and the "base people" and on the five categories of the latter (Sansom 1934:145-147).

Ryō no gige 8-42

Apparently marriage between good and base people was not prohibited, for Article 42 of Ordinance 8 (Households) of Ryō no gige makes the following provision for the status of children born to such alliances made without the good person's knowledge of the base person's status (structural translation mine).

令義解、8 戸令、42 為夫妻条

Kanbun官戸陵戸家人公私奴婢。与良人為夫妻。所生男女。不知情者従。皆離之。其逃亡所生男女。皆従。(SZKT RG:105)

Japanese translation   官戸、陵戸、家人、公私の奴婢(公奴婢・私奴婢)が、良人と結婚して生んだところの男女は、賎であるとの実情を知らなかった場合には、良人に属させること。皆、離婚させること。逃亡して生んだところの男女は、皆、賎に属させること。

Structural translation   Always: Where [1] [a member of] an official household [official servant], or [2] [a member of] a tomb household [tomb tender], or [3] a house person [clan or family servant], or [4] a public [government] or [5] a private male slave or female slave, and a good person have become husband and wife, there is born a man or a woman, [when] [the good person] did not know the circumstances [of the base person's status], [the man or the woman] will follow [conventions for] [be treated as] [be affiliated with] good [people]. All [spouses found to have married in such ignorance] will separate. Where [the husband and wife] have fled and flown there is born a man or a woman, all [such offspring] will follow [conventions for] [be treat as] [be affiliated with] base [affiliates].

Sansom's translation (Sansom 1934:147, brackets in original)

42. When a slave is married to a free person, children born of the marriage shall, if the marriage was contracted without knowledge [that one party was a slave] follow the status of the free party. The parties shall be separated.

Where [one of the parties] has absconded and a child is born, it shall follow the status of the unfree party.

Comments The commentaries do not agree on the meaning of this second clause; but it seems that absconding was taken as showing that the parties were aware that one was a slave.

Ryō no gige 8-43

Article 43 provides that, in the case of a man or a woman [person] who was born in a situation where a house servant or male slave committed an indiscretion (奸 = ?) with the master or someone five degrees or higher (four, three, two, one) of relationship to the master, will "sink to the government" (凡家人奴。奸 [= ?] 主及主五等以上親。所生男女。各没官。SZKT RG:105). In other words, such people will be ascribed to one or another base status, and whatever land or other property they may have inherited will go to the court.

However, the commentary to Article 43 states that, in the case of rape (強奸), such offspring will be treated as "good people" (良人. They will also be treated as "good" should the master and the slave not have been aware, until after their indiscretion, that their status relationship was not suitable, according to the codes and abiding by the provisions for not knowing the law at the time of the crime.