This is the review up until chapter 3 of the light novel and not the web novel. There might be spoilers here as well >_<
I've read tons of NTR, from you-know-where and when I heard about this, I was reluctant at first because NTR is just depressing and ruins most of my day. But after some time I decided to give it a try and I have to say, I've enjoyed it. Like, it's satisfying to know that the guy who's being NTR'ed thinks to do something and not just stays blankly without even saying a word about it.
The characters are pretty interesting as well, though in three chapters I have yet to come to support the mc, Yuu Isshiki, for now. I know it's still early but as far as I can see, a lot of stuff might be happening because of him as well. But the bad guys, in this case, his girlfriend, Karen, and senpai, Tetsuya, with whom she is having an affair, have a character personality that you might really come to hate as well. Like, Karen is all cutesy type of girl who wants to have dates with more "chic" and that cute personality that we kind of love in normal romcoms, is pretty annoying here and you just want to say "f*ck off, girl!". The same goes with Tetsuya as well. He's a handsome and smart guy with pretty twisted thoughts that I think are better to see in person in the novel rather than me saying cuz I won't be able to explain properly, lol.
Kouko senpai is the best I'd say, I think she's gonna become the main pillar for the changes in Yuu's personality and thinking. It's seen pretty clearly in these few chapters that I've read right now. Kouko is a person that you don't really see a lot in these types of stories and plots and for me, this was kind of refreshing and really cool as well. I wish I could elaborate more but this is my first time reviewing and I dunno how to really explore deep into a character but this is how I felt when I read for the first time and said this in words.
tl;dr, I think it's worth a try, the story's interesting, and the plot has many things that are about to be fun from what I can see right now after reading three chapters.