Yeah, those two work of in the same stereotypes but shimotsuki it's actually about escaping the romcom tropes and living a normal boring happy life, you'll get what I mean if you read vol 5 of the novel.Need me to reread few times but I finally got it, thanks.
On a side note, have you read Nyanta to Pomeko? This is sudden, but I think they are a little similar in a way. Rather than just leaving the MC, they "betray" him and there is no "antagonist"(or well, the girls are the antagonist in MC's eyes). It's a bit heavy and psychological story. There is a manga, but it's ended while leaving some story untold. The wn have more content, but currently on hiatus.
Idk why this even turned into a recommendation, but reading all of this reminds me of it.
(speaking of Nyanta to Pomeko, there is also a story that probably inspired it called The Girls who Traumatized Me. Despite the title, it is actually lighter than the former. Though, I haven't read much of the novel).
Also on nyanta and pomeko you're totally right, I was shocked to know the WN was so short and didn't had a conclusion either, some of the parts that didn't get adapted to the Manga were the ones I liked the most.
Also the usual "f those bitches for betraying mc" crowd would have despised how those went, this are stories about healing and moving on, not really revenge.
nyanta's sister who was probably the worst of that bunch but she's the one who works her ass off to get redemption getting the other girls to back off and getting that Mc the grandpa's house, etc. that's why it felt good that Mc fully forgave her at least, it's kinda what will happen in shimotsuki too but less intense. Or siscon/brocon vibey.