ML's father is the culprit and Mi Sook is his mother. My prediction, our male lead will discover this soon and he'll struggle with telling Yoon Young. I wouldn't be surprised if he chose to sacrifice his existence in order to put the right person behind bars and give YY her mom back.
Phew...I'm relieved to see that this has 16 episodes! Lots of dramas lately have been ending with 12. I thought we were in for a rushed ending. I'm glad we still have a few weeks left.