In Japan, the minimum age for marriage is 18 for men and 16 for women. However, minors, those under 20 years of age, need parental consent to marry. The consent of only one parent is sufficient in cases where the other parent is unknown, has died or is unable to indicate intent.
Foreign couples that live in Japan are allowed to marry in Japan just as any ordinary Japanese citizen would be allowed to. The foreign couple needs to register their marriage at the local government office and both parties will need to submit a certificate of legal capacity to marry along with Japanese translations. Completing these procedures will legally marry the couple under Japanese law.
The only major requirement for keeping a spousal visa in Japan is to continue to stay married to a Japanese national. In general, spousal visas do not apply to couples who divorce or where one spouse has died, although it may be possible to switch to a long term visa in some cases. It is important to note that, even if the couple is legally married, they must also meet a certain standard of marital behavior and marriages that seem fraudulent risk the possibility of having a renewal visa rejected.
Under the citizenship by parentage system, as long as one of the child’s parents is Japanese, the baby is entitled to receive Japanese citizenship. The birth of the baby must be registered with the local government office or, if overseas, at the Japanese embassy or consulate. However, simply being born in Japan is not enough for a baby without Japanese parents to acquire Japanese citizenship.