The author isn't good at character development, she isn't even good at developing characters in general. She just writes for the mases. See at Jaek this chapter, no remorse whatsoever, he is still only thinking about him, his needs and what he wants, even if its inconvenient to everyone around him. He doesn't care for Dan either, he wants to dominate him. And the second he gets what he wants he would leave Dan with no remorse, sadly this is a "romance" manwha, so that would not happen, but that's how people like him act in real life, they will end up together. The kind of "love" the author portrays is toxic and no even realistic
And here I was expecting for some character development