A female teacher is blackmailed into having sex with her student. The student is pudgy, and wearing glasses. The teacher's sister is has sex with their father, and eventually so does the teacher. I remember reading the premise, and it said something about the whole town being in on it. Please help. I want to ensure how it ends t

Don't ring a bell but maybe something by SANBUN Kyouden, he love incest, NTR and whole town scale hentai.

Hmmm...it wasn't any of these, plus they don't match the art style

Sorry, I don't specifically remember that either.......take a look at these few.....Tada Koishikute, Aitakute..., Ou-sama App, Toraware Box.....these are the ones that have had the most recent releases that at least have the same themes (female teacher being blackmailed) and look like they have enough translated to English content to account for all the events you're describing (you're talking about at least three full sex scenes.....teacher-student/teacher's sister-father/teacher-father) so it's got to be at least a part of a tankoubon or a number of anthology chapters.

I can come up with a list of a little over 50 possibilities (at least 35), but it's a list on another site, I can't link it here. PM me if you want.

Good luck finding it

Oh, and yeah, I love Sanbun Kyouden, and I'm not sure he's ever had a female teacher character.......funny, but of course I might just be forgetting, his beautiful, full-bodied but kinda empty-headed female leads do tend to become kind of cookie-cutter after a while