I think he was just pretending that he didn't noticed that they should break up. He was mature but not when it came to the seme cause with him they were always stuck in the past. He was glad that he could monopolize the seme and that the seme gave up everything for him in a way he could think like "see that? He did all that for me I'm special" cause it was like his way to believe that he was being loved by the seme that was loved by everyone (cause the seme was incredibly popular and talented and handsome and kind almost like a perfect person so it was like "that person that everyone loves loves me cause I'm special") he also realized with time that this was destroying the seme and was terrified of losing him but also terrified of the seme losing himself and I guess that when he saw the other MC (our lovely big bear) he was once again terrified of losing him so he acted hostile but then he finally realized that there's was nothing he could do to bring happiness to the seme and that in fact he was only bringing him pain so he decided to let it go for the sake of both of them since both of them could no longer be like in the past and couldn't be happy together anymore.
I guess you are confused because while reading yaoi/shounen ai we are not used to this kind of character development
Honestly, I didn't think about that "this special person that everyone loves thinks Im special and loves me" part. Now that I think about it I think in suh suffers from a pretty bad case of inferiority complex. But yeah I get what you mean, thank you for sharing your opinions with me.
I mean you are not wrong, most of character development I've come across in bl has something to do with abuse either physical or emotional or has to do with having a hard time trusting people. I think this bl really showcases how to write a good breakup scenario which although a bit idealistic it's not unrealistic.
Honestly the more I read this the more confused I become about in suh (I think that's how you write his name? I don't remember). I can't understand him and what he is thinking no matter how hard I try. I don't know if I like him or not and I don't even know what his intentions are. One time he comes off as selfish and the other as selfless, immature and then mature, conceited but then genuinely caring.
All in all, this discourse inside of me confuses me about whether or not I believe he is well-written because I can't tell if his behaviour constantly contradicts itself on purpose or on accident like it was a mishap from the writer.
Maybe he is that well-written, written with a lot of layers, written with complexity in mind or maybe I am overthinking it.