Can a woman have sex with a man as a marriage?

Marriage is a marriage in which a man and a woman voluntarily combine by talking to themselves or introducing themselves and get a marriage certificate. Other circumstances, such as two people living together, can only be regarded as voluntary, not as marriage. Because it has not been recognized by law, even if it has been held, it will not work in a big sense. As for some people who say that you are married, it is unreasonable. After all, there is no marriage certificate in your personal information.