It's a great story, but i get the feeling it'll make you sick to your stomach. The old man wins at every turn so far, so if you can't stomach the evil grinning and manipulation i'd pass. Just know that he doesn't do it for no reason, not that it is necessarily justified... Kyunghee used him for money and then when he went to further their relationship Kyunghee threw him away. He's basically decided to use force and blackmail at this point. You can see at one point that he's not happy having to blackmail Kyunghee, but the depths he goes to to keep Kyunghee bound to him are disgusting indeed. He even uses Kyunghee's mom.
I read the first chapter months ago and I was disgust by it ... but I can't forget this story I don't know why. I look up people's comments but never have enough courage to read the story myself.