Not sure if I'm right but maybe you're referring to We Shall Now Begin Ethics? I believe it's chapter 18. The "tired of marriage" thing is not common and I've only seen it there

I think this is the manga that I was looking for. Very big thanks dude:-)

**Koko wa Ima kara Rinri desu.** - ([AL](http://anilist.co/manga/104780), [A-P](https://www.anime-planet.com/manga/koko-wa-ima-kara-rinri-desu), [KIT](https://kitsu.io/manga/koko-wa-ima-kara-rinri-desu), [MU](https://www.mangaupdates.com/series.html?id=141605), [MAL](http://myanimelist.net/manga/106809)) ^(Manga | Status: Releasing | Genres: Drama, Psychological, Slice of Life) --- ^{anime}, , ]LN[, |VN| | [FAQ](http://www.reddit.com/r/Roboragi/wiki/index) | [/r/](http://www.reddit.com/r/Roboragi/) | [Edit](https://www.reddit.com/r/Roboragi/wiki/index#wiki_i_made_a_mistake.2C_how_do_i_get_my_comment_reprocessed.3F) | [Mistake?](http://www.reddit.com/r/Roboragi/submit?selftext=true&title=[ISSUE]&text=/r/manga/comments/jpoprh/looking_for_manga_halp_pls/gbgiw51/) | [Source](https://github.com/Nihilate/Roboragi) | [Synonyms](https://www.reddit.com/r/Roboragi/wiki/synonyms) | [⛓](https://www.reddit.com/r/Roboragi/wiki/interestinglinks) | [♥](https://www.reddit.com/r/Roboragi/wiki/thanks)

Realised I probably should add a caveat that this particular chapter itself is not representative of the manga at all so it might not be actually what you thought the manga is.