Animeonlineninja Fuufu Koukan Modorenai Yoru Work [upd] -

The narrative kicks off during a joint vacation to an onsen spa. What starts as a standard getaway takes a dramatic turn when the couples decide to engage in a "marriage exchange". This decision leads to a night that changes their relationships forever—the titular "Night of No Return." Key Characters

It looks like you're trying to search for a specific adult anime/doujin title, but the phrase is a bit mixed. animeonlineninja fuufu koukan modorenai yoru work

On Reddit and MyAnimeList forums, Fuufu Koukan: Modorenai Yoru is described as "the OVA you watch once and wish you hadn't." Common reactions include: The narrative kicks off during a joint vacation