noun
common-law couple; couple in an illicit union
Refers to a couple living together as if married without legal registration, often with a nuance of an improper or secret relationship. The term can carry a slightly old-fashioned or judgmental tone.
彼らは馴れ合い夫婦として十年以上一緒に暮らしている。
They have been living together as a common-law couple for over ten years.
昔は馴れ合い夫婦は世間から白い目で見られた。
In the past, couples in illicit unions were looked down upon by society.
Compound of 馴れ合い (nareai, 'collusion, secret understanding') and 夫婦 (fūfu, 'married couple'). The exact historical derivation is uncertain, but the term suggests a couple whose relationship is based on an informal, possibly improper, agreement rather than formal marriage.