I don't know, man. Trust comes from both ways, the thing is, it's easy for us readers to comment something like this because we haven't actually experienced it through their, the character's, own perspective. The seme didnt know uke's past. And if you look at it, clearly, the uke also feels insecure. I've a seen a whole lot of mangas with childish semes, and this aint it, man. And lastly, the seme never thought anything about the uke's sexual endeavors/behaviour, and that says a lot :) I wouldn't say he's obsessed too because he never forced the uke nor did he ever go past any boundaries.
But he is a slut tho? He sleeps around thats what a slut is having alot of casual sexaul relatinship. The thing giving mixed signals he says he likes him then proceeds to tell him he doesnt want too after trying to sleep with him , of course the Seme is confuse
Seme still behaves immature. He isn't stable at all. Uke was heartbroken in the past. Imagine his lover leaving him for a woman. I don't think seme was initially gay, he is just obsessed with saku. That isn't enough. The uke wanted to feel secure but seme make him feel secured. Because he would have thought he would do the same as the ex. Once bitten twice shy..... And he is the owner of his body not the seme.....stop slut shaming..... Isn't it better than using seme for sex, he goes out for his sexual needs....