
I liked it very much, but I still don't get their feelings, the entire manhwa I was confused but still liked it(?) so I kept reading it. And I seriously don't get the end =_="... was it open for ou own ideas and to us to decide how it ends or it ended with them entering that hell-like relation ship? Idk but I'm satisfied I guess.

According to multiple comments on this site, a few of them claimed to have reliable level of knowledge on psychology( Im not certain, as I've never met them) combine with my own opinion, I'll tried to explain the ending to you.
I think kyung soo went back to Yule in the end, but not because he loves him, but because of guilt. The flashback in the end with kyung soo saying " Now that I've hurt a good guy like him( Dong Hyung), I will never be happy again ". As we see in the earlier chapter, kyung soo cried and asked Dong hyuk " Did I make you like that? " after he gets back with dong hyuk and discover that Dong Hyuk had changed for the worse, and Kyungsoo think its was because of him. In one chapter, we see kyung soo reminded of Yule's brother( the motherf$&king asshole) saying that " Something about you( Kyungsoo) make people angry " ( which is complete bullshit that the brother makes up to justified his abuse on this sweet boy) and Kyung soo started to believe that because everyone around him seems to want to abuse him. And then when we got kyung soo at the end, tired, weary, traumatized, and guilt riddance. So when after everything Yule still don't fucking leave him alone, he just decided to give up cuz he's too tired to run. In short, this is probably what kyung soo think at the end " you hurt me and I hurt Dong Hyuk, we're both don't deserve happiness,so let's just be unhappy together".
Ok, mas o que caralhos? Sério... jdksksks kakakaka ok agora vou fazer dever :P