Article 24. Marriage shall be based only on the mutual consent of both
sexes and it shall be maintained through mutual cooperation with the equal
rights of husband and wife as a basis.
With regard to choice of spouse, property rights, inheritance, choice of
domicile, divorce and other matters pertaining to marriage and the family,
laws shall be enacted from the standpoint of individual dignity and the
essential equality of the sexes.
Although the age of majority is 20 years, women at age of 16 or over and men at age of 18 or over can get married if they have their parents' consents(The consents are required if they are under 20.).They do not have to acquire both of their parents, and if one of their parents disputes their marriage, they can get married with the consent of another parent.
In the case where one of parents can not express his/her intention clearly, the same will be applied.
When a couple files a notification of marriage, the marriage becomes effective in Japan. The religious ceremony is not required under Japanese law although many Japanese couple like to hold marriage ceremony in Christian manner.
Regarding "mutual consent of both sexes", it is sometimes said that same sex marriage is prohibited in Japan . But it is possibly not true because the main meaning of these words is that marriage should be made not by intention of a patriarch or only by that of a man.
In Japan discussion on same sex marriage has just begun.