Civil Code

Marriage may not be entered into until a person has reached the age of 18.

A person who has a spouse may not enter into another marriage.

Lineal blood relatives may not marry, nor may collateral blood relatives of up to the third degree of kinship; provided, however that this does not apply with respect to a marriage between an adopted child and a collateral blood relative through adoption.

The preceding paragraph also applies after kinship is terminated pursuant to the provisions of Article 817-9.

Lineal relatives by affinity may not marry. This also applies after relationships of affinity are terminated pursuant to the provisions of Article 728 or Article 817-9.

Even after the termination of kinship pursuant to the provisions of Article 729, marriage is not permissible between the adopted child, the spouse thereof, the lineal descendant of the adopted child, or the spouse thereof, and the adoptive parent or lineal ascendant thereof.

A marriage becomes valid when an application to register the marriage is filed pursuant to the Family Register Act (Act No. 224 of 1947).

The application referred to in the preceding paragraph must be filed using a paper document bearing the signatures of both parties and no fewer than two adult witnesses, or must be filed orally by these persons.

It is not permissible to accept an application to register a marriage until the marriage has been found not to violate the provisions of Article 731, Article 732, and Article 734 through Article 736, the provisions of paragraph (2) of the preceding Article, or the provisions of any other law or regulation.

If two Japanese nationals in a foreign country seek to marry, they may file an application to register their marriage with the Japanese Ambassador, Minister of the Japanese Embassy, or Consul stationed in that country. The provisions of the preceding two Articles apply mutatis mutandis in such a case.

A marriage is void only in one of the following cases:

if the parties did not have the mutual intention to enter into a marriage due to a party being mistaken as to the identity of the other or any other such cause; or

if the parties have failed to file an application to register the marriage; provided, however, that if the application to register merely lacks a formality prescribed in Article 739, paragraph (2), this does not impair the validity of the marriage.

A marriage may not be canceled other than pursuant to the provisions of the following Article, Article 745, and Article 747.

Either of the parties, their relatives, or the public prosecutor may request the family court to cancel the marriage if it violates any provision of Article 731, Article 732, or Article 734 through Article 736; provided, however, that the public prosecutor may not request this after the death of one of the parties.

With regard to a marriage that violates the provisions of Article 732, the spouse in the previous marriage may also request that the marriage be canceled.

It is not permissible to request that a marriage violating the provisions of Article 731 be canceled once the person that was not of marriageable age reaches marriageable age.

A person formerly not of marriageable age may request that the person's own marriage be canceled within a further period of three months after reaching marriageable age; provided, however, that this does not apply if the person ratifies the marriage after reaching marriageable age.

A person who has married due to fraud or duress may request the family court to cancel the marriage.

The right to cancel a marriage as under the preceding paragraph expires if, after discovering the fraud or escaping from the duress, the party allows three months to pass or ratifies the marriage.

The cancellation of a marriage has only prospective effect.

A party who did not know of the grounds to cancel at the time of marriage must make restitution for property gained as a result of the marriage, to the extent of the benefit that that party retains.

A party who had knowledge of the grounds to cancel at the time of marriage must make restitution for all benefits obtained as a result of the marriage. In such a case, the party with knowledge is liable to compensate the other party for damage if the other party entered into the marriage in good faith.

The provisions of Article 728, paragraph (1); Article 766 through Article 769; the proviso to Article 790, paragraph (1); and Article 819, paragraphs (2), (3), and (5) through (7) apply mutatis mutandis to the cancellation of a marriage.

A husband and wife take the surname of either the husband or the wife, as decided at the time of marriage.

If one party to a marriage dies, the surviving spouse may revert to the surname used before the marriage.

The provisions of Article 769 apply mutatis mutandis to a case as referred to in the preceding paragraph or Article 728, paragraph (2).

A husband and wife must live together, cooperate with each other, and act so as to be of assistance to each other.

Unless husband and wife enter into an agreement setting forth otherwise with regard to their property before filing the application to register the marriage, their property relations are as prescribed in the following subsection.

If a husband and wife have entered into an agreement that departs from the statutory property system, the agreement may not be asserted against the successor in title of the husband or wife or against a third party unless it is registered by the time that the application to register the marriage is filed.

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The property relations of a husband and wife may not be modified after registration of their marriage.

If one party to a marriage manages the property of the other and imperils that property through mismanagement, the other party may file a request with the family court to personally manage that property.

A claim may be filed for the division of property held in coownership together with the claim referred to in the preceding paragraph.

If the person managing the property changes or property held in co-ownership is divided pursuant to the provisions of the preceding Article or as a result of the agreement referred to in Article 755, this may not be asserted against the successor in title of the husband or wife or against a third party unless it is registered.

A husband and wife share the expenses that arise from their marriage, in consideration of their assets, income, and all other circumstances.