I personally hate rape and blackmail, and the first volume of this is always in the back of my mind when I read this. However, I do think that not only does the seme change, but so does their relationship. Also, some volumes later the seme does address what he's done and feels genuinely bad about it.
I personally really like it, and I think the author does a good job of tackling the relationship problems they face (especially in vol 9).
I don't know about the pacing or how long it takes bc there are other couples and stuff that are mixed in
You should definitely give it another shot. Eventually the rape DOES get talked about between the two of them and the seme feels like a piece of shit for how he treated the uke. Their relationship grows spectacularly and the seme has great character development! I think it's worth it for you to try reading it again. Out of everything I've read, this is my number one favorite.
The seme is literally a dumbass at first cause that’s the only way he could express his “love” but as the story continues he starts developing and changing for the uke and has morals and you get to love him, they do address what happened in the past when they first met later on, but I fell in love with this manga I recommend reading it again :)

So, I read this maybe a year ago, but could never finish it bcs the seme is a jerk and the uke felt defenseless. Their relationship started from rape and blackmail. Now, I've read alot good yaoi where the relationship starts from rape, but I don't know about this... Does the seme change later? If yes, how long does it take? Does it get any good?