Oh also remember the uke being the feminine type, and I want to say the manga was on the older side. It was not a comedy manga, the rest of the story was 100% serious and it was so out of left field that it made me laugh so hard.
I think it might be Abaite, sono me de
https://www.mangago.me/read-manga/abaite_sono_me_de_uncensored/
Hmm not seeing the sound effect. I'm a big fan of that one though!
Actually think you might be right. Did some more digging and I found the chat about the scanlators talking about the sfx being "fart" in the photos (second to last page) and someone commenting about it being wrong: https://www.mangago.me/home/mangatopic/20079335/ Looks like it's been fixed, though. Still not sure if it's the exact one I'm thinking of, but it can't be that common of a thing, so I'm thinking this has to be it lol. Thank you!
I remember reading a manga where there was a sound effect of him farting or tooting while they were having sex, it was towards the end of the manga and I remember there being a translator note saying yes, that's really what it says. Anyone else read it and remember what it was?