I've figured out the target audience. Japanese men who had poor experiences with the "popular" highschool girls and want to experience sexual revenge against them through this manga.
I don't know any other reason to read this other than just to read the MC's suffering for the most part. Even the more heartwarming parts can be interpreted as a soft spite towards the MC. For example, her pandering Sumo is basically their idea of "hah, you would never do this IRL, but you're forced to now because he saved literally saved your ass!" Even the soft spoilers from the author and the comment section suggest her new love interest will probably develop in the direction of "she likes him, but in attempting to get to know him, she encounters more suffering and overall not a good end (maybe not a strictly bad one either, but it probably won't be a strongly net positive development)".
This manga is like a 3.5/10 at best for me. It's actually quite bad given there isn't much reason to read it other than to read MC's suffering. I did get roped into it since it was initially interesting as a bit of an out of the ordinary take, but the takeaway I've gotten from it leads me to believe it's just torture porn (almost literally) with some soft bits to reset your palate (and still be pandering to it's targeted audience at the same time). You could say I'm projecting, but I do feel that the erotic scenes were mainly focused on suffering and the MC's mentality during them, rather than aiming to generically arouse people. I'm not into MC's suffering, so there's nothing here for me. Subjective nor objectively.