No wonder he's so nice to Kim Dan's grandmother. 

That was the longest introductory chapter I have ever read. Even though the translation was average and lacked some context, it was still a pretty good first chapter. This seems promising. 

 Your obsession with your sister is disturbing . It seems like you’re trying to convince yourself that she is just your sister and not something more.
 

That mistress of a sister makes me think of the mistress's best friend from "Marry My Husband." Same vibe. 

Wow! He arrived way too quickly. I appreciate the timing, but I would have liked to see him struggle a bit more to really understand what a terrible person he is. It would have been nice to see him grovel.