Well, technically, Eunwoo was never actually manipulative, arrogant etc etc. In fact, he admitted it himself during the later chapters that he was only acting like that to protect himself and because he didn't know how else he could keep Wonho close to him. He basically acted like a jerk to have an excuse to see him and be with him in the only way he thought he could.
If you prefer describing manipulation as being a jerk so be it, but I think at the end of the day my point stands. If you have the stomach to be a jerk to the person that you supposedly love just to keep next to you , that shows a very toxic personality. He is not going to stop being that way. And he was not only being a jerk to the one he "loved" but to others too. I don't believe in romanticise jerks personally but like I said, that is just my personal opinion
I have to say this was not that great for me. The first couple was ok, and I like that Min ki decided for the healthy relationship. About the second couple, I guess my problem is that I did no really bought the characters development. Eununwoos changing from manipulating to loving boyfriend in one illuminated moment was not very believable to me. Maybe this is because sadly I witnessed some toxic relationships in the past and, although people can improve , I haven't seen such a drastic switch in personality like ever. But this is just my personal experience I'm sure this was really good for a lot of people.