also: ムコようし
noun
adopted son-in-law; son-in-law taken into the family
A man who marries into his wife's family and is adopted as their son, often to carry on the family name or business. Common in traditional Japanese family structures.
彼は婿養子として妻の家に入った。
He entered his wife's family as an adopted son-in-law.
婿養子の制度は、
The adopted son-in-law system is sometimes used to continue the family name.