Can anyone tell me if this has good emotional payoff or if the seme changes?

Don’t bother, the spoilers basically show this to be even trashier than it already is.
Rape fest galore

there is a lot of rape, but it is written sexual or romantic at all, but rather clinical; it's basically to show how awful and unlucky his life is. there is a plot outside of the rape, and character development (altho it is more accurate to say downward spiral bc it gets progressively worse for mc). seme never touches mc after the first arc, until mc initiates much later. it's hard to say seme changed bc imo the only change is that he fell for mc; it's more like a gradual unraveling of his character and motivations... but he does make sacrifices for mc bc he loves him, even while pretending he doesn't. he's a genuinely well-written "black flag" character. i kinda have a love-hate thing for him. there is some payoff when mc gets his revenge, but it's eclipsed by the tragedy he faces. the whole thing is essentially misery porn/drama with some catharsis, but if u are curious about a raw and gut-wrenching exploration of stockholm syndrome, id rec reading the novel instead.