noun
couple who only go through the motions of being husband and wife
Describes a married couple who maintain the appearance of a normal marriage in public but lack genuine emotional connection or intimacy in private.
彼らは周りからは仲良く見えるが、実は仮面夫婦だ。
They look like a close couple to others, but in reality they are just going through the motions.
Compound of 仮面 (kamen, 'mask') and 夫婦 (fūfu, 'married couple'), literally 'mask couple'. The exact origin is uncertain, but it likely emerged in modern Japanese to describe marriages where the couple hides their true relationship behind a facade.