That's the thrill cause it's a mystery that will unfold later.
But the mystery ain't helping the image of the seme much, I mean he wasn't likeable from the very beginning cuz of all the stuff he did to the uke but they made it worse by making it a mystery and tbh I don't find it thrilling I find it more confusing cuz how the hell did they even get in a relationship to begin with? how did the seme ask the uke to go out with him and why did the uke accept it? didn't the seme's ex the one being obsessive but how on earth did the seme become the obsessive one in his story? It's like they uno reverse the seme's character out of nowhere
I know why he's obsessive, He clearly showed it since he saw his Paintings That's why he wanted to get closer to him and fucked his GF to split them up and that was his opening. It clearly showed his Posessiveness through his actions not by Words So I think that's why you're confused and they started going out when he finally let go of his GF and wanted to get along with him
I feel like we skipped some chapters cuz the seme feels like an uno reverse, can't explain it properly but I feel like there's a hole over here, over there, there's just so many holes