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's 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 6 months of the marriage. In a family register, a foreigner doesn't have their own entry, while he / she can be recorded in it as a spouse, for example. 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 6 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