The main family law of Japan is Part IV of . The contains provisions relating to the and notifications to the public office.

Background

The ie (家) or "household" was the basic unit of Japanese law, from the founding of the Meiji Civil Code in 1896, until the end of World War II: most civil and criminal matters were considered to involve families rather than individuals. The ie was considered to consist of grandparents, their son and his wife and their children, although even in 1920, 54% of Japanese households already were nuclear families.

This system was formally abolished with the 1947 revision of Japanese family law under the influence of the allied occupation authorities, and Japanese society began a transition to a more Americanized nuclear family system. However, the number of nuclear families only slightly increased until 1980, when it reached 63%, and the Confucian principles underlying the "ie" concept only gradually faded and are still informally followed to some degree by many Japanese people today.

Marriage

Marriage of Japan's formality takes the form of civil marriage. A marriage is effected by filing notification of it. (Act No.89 of 1896): Part IV: Chapter 2. The last effective revision was enforced on 1 January 2007. A wedding ceremony performed by a religious or fraternal body is not a necessary element for a legal marriage.

According to Articles 731–737 of the Civil Code, A man before attaining 18 years of age, a woman before attaining 16 years of age, may not marry. (Article 731) A minor shall obtain the consent of at least one parent to marry. (Article 737) Bigamy is prohibited. (Article 732) [declared unconstitutional in 2016 by the Supreme Court: A woman may not remarry within six months of the day of dissolution or cancellation of the previous marriage, except the case in which she both gets pregnant before the day and gives birth to the child. #1 (Article 733)] Lineal relatives by blood, collateral relatives within the third degree of kinship by blood #2, may not marry, except between an adopted child and their collateral relatives by blood through adoption. #3 (Article 734) Lineal relatives by affinity may not marry. #3 (Article 735) An adoptive parent or a lineal ascendant of an adoptive parent may not marry with an adopted child, their spouse, their lineal descendant, or a spouse of their lineal descendant. #3 (Article 736) It is considered that this remarriage prohibition is to avoid confusion as to the identification of the child's father. between one and one's sibling, uncle, aunt, nephew, niece by blood. It may be a case in which this prohibition shall apply after the termination of a family relationship between the two parties.

If one or both in the couple is a Japanese national, the marriage is recorded in a family register with one concerned Japanese at its head.

It is a rule in principle that the two shall have the family name in common following their marriage. However, if one of them is a non-Japanese, this rule does not apply. They can use one of the spouse's names as their family name or keep their names after marriage. If a Japanese spouse changes their family name to their spouse's, the name change must be filed within six months of the marriage.戸籍法第107条第2項外国人と婚姻をした者がその氏を配偶者の称している氏に変更しようとするときは、その者は、その婚姻の日から六箇月以内に限り、家庭裁判所の許可を得ないで、その旨を届け出ることができる。 Family Register Act Article 107 paragraph 2. If a person marries with a foreign national and chooses to change the family name to the foreign national's, the person may file to that effect, waiving the permission of family court, within 6 months of the marriage. A foreigner does not have an individual entry in a family register; however, they may be recorded in it as a spouse.Ito, Masami, "Marriage ever-changing institution", Japan Times, November 3, 2009.

International marriage

Children

Paternity A child born to a married woman is assumed to be the child of her husband, although her husband may file in family court to disavow paternity if the paternity of the child is questioned. If a child is born to an unmarried woman, or if paternity is disavowed by the mother's husband, the father may later claim paternity through family court proceedings, or the child may file in family court to force his or her father to be recognized as the father.

Children are given the family name of their parents at the time of birth. If the father is unknown at the time of the child's birth, the child is given the family name of the mother, but may have his or her name changed to the father's family name after the father recognizes paternity.

Adoption Child adoption in Japan is relatively uncommon, mainly due to lack of government support and legal trouble encountered from the child's birth parents. In Japan, even if a parent is legally unfit to see their child, the parent is still the child's legal guardian and their consent is required for everyday decisions, such as the child's education or field trips that may pose safety concerns. This is an issue even for parents looking to adopt because a child adopted over the age of six will still be registered in their birth parent's koseki, as written in Article 817-2 of the Japanese Civil Code. As a result, if parents want a special adoption, where the child is registered under the new parent's koseki, the child has to be under the age of 6.

There are two main places to apply to for adoption. The first is a religious adoption agency. These private agencies are allowed to charge a fee for the adoption process, as opposed to the process being free through the government.

The other is the local Child Guidance Center, which is a government agency. In 2010, United Nations Convention on the Rights of the Child noted that the CGC staff did not seem to be properly trained to work in child services and did not seem to be promoting adoption. In 2016, the Child Welfare Act was revised to explicitly state that the CGCs were responsible for the adoption process. Furthermore, when adopting through government agencies, prospective parents must be Japanese married couples.

Surrogacy and reproductive technology

Surrogacy Although there is no law banning birth by surrogacy in Japan, there is a strong stigma against it. "Japan's first surrogate birth was announced in 2001 and led to the Health Ministry calling for an immediate ban. Although this was blocked, the Society of Obstetrics and Gynecology successfully managed to prohibit [its members from conducting] surrogate births in 2003, citing the mental and physical burden to the surrogate mother and the fear that surrogacy could confuse familial relationships."

As a result, Japanese couples tend to seek surrogate mothers abroad. However, "current law in Japan states that the mother of a child is the one who gives birth to the baby," and that children must be registered in the koseki (family registry) to be a Japanese citizen. Since the surrogate is not Japanese and the father is not the surrogate's legal husband, the legal status of children born via surrogates may end up in question. A famous case of this issue is that of the Japanese actress, Aki Mukai, who had twin sons through an American surrogate mother in 2003. The boys only had American citizenship, which resulted in a series of court cases that ultimately culminated in the Supreme Court concluding that surrogacy was ethically wrong and Mukai had to adopt her sons to be considered their mother.

In 2005, a Tokyo-based sperm bank called Excellence began offering surrogate mothers and assisted conception services in South Korea to Japanese couples. At the time, it was the only Japanese company known to provide such a service, according to Excellence's head Yuji Sasaki.

In 2006, a doctor enabled a 61-year-old woman to carry the child of her daughter who was unable to give birth herself after cancer treatment. "The procedure was performed at the Suwa Maternity Clinic by Yahiro Netsu, a long standing supporter of surrogacy procedures. In a statement issued to the press, it said: 'The clinic hopes that Japan will hold forward-looking discussions on surrogate births and that it will take place in Japan without abuses.'" In light of this procedure, "then-Prime Minister Shinzo Abe told reporters that the issue of surrogacy is 'very difficult' and Sanae Takaichi, state minister for gender, equality and population has said that 'the discussion is highly welcome, but it is extremely difficult to judge whether surrogate birth can be encouraged.'"

In 2008, Manyi Yamada was born using donated eggs, the sperm of a Japanese man Ikufumi Yamada, and an Indian surrogate mother. Yamada and his Japanese wife divorced before Manyi's birth and the latter withdrew her consent to adopt Manyi, which left Yamada's application as a single father unlikely to be accepted. An Indian child welfare charity Satya petitioned unsuccessfully to gain custody of Manyi, claiming that "'they have violated Indian laws by not signing a surrogacy agreement and taking custody of a child abandoned by its mother.' The Japanese Justice Minister, Okiharu Yasuoka, indicated to reporters that he would consider granting Manyi a visa but that the legality of the birth was something that would need to be addressed in the near future. 'Whether to permit surrogate pregnancy is a matter to be discussed by respective institutions...The ministry will study the possibilities under the law out of consideration for the child's future.'" Ultimately, the Indian Supreme Court granted custody of Manyi to her grandmother Emiko Yamada.

"The son of a wealthy IT entrepreneur, Mitsutoki Shigeta attracted controversy in 2014 after Thai officials raided his flat in Bangkok on suspicion of human trafficking and found at least nine babies, nannies and a pregnant woman." He was quoted as saying 'The best thing I can do for the world is to leave many children,' and as hoping to father between 100 and 1,000 babies. "The case, which became known as the 'baby factory' scandal in the press, cast a spotlight on Thailand's surrogacy industry and the Thai government shortly afterwards introduced a ban on foreigners from paying for surrogacy in the country." A year later, the Thai "Women and Child Welfare Protection Bureau, which is currently taking care of the children, has confirmed that six of the surrogate mothers, three of whom gave birth to twins, are seeking custody," their lawsuit alleging that the bureau is failing to adequately care for the children. By 2018, however, the women had forfeited their rights to the children and the Thai court had awarded paternity rights to "the Japanese businessman"—mostly likely Shigeta—who had fathered them. An additional six babies had also by that point been identified as having been fathered by Shigeta, bringing the total identified so far to 17. A 2018 CNN report revealed that Shigeta has two additional children born to surrogates in India.

IVF and artificial insemination

Rumors that Empress Masako of Japan had undergone IVF treatments were reported by the UK's The Independent in 2001.