It's an interesting premise that tripped and rolled down the stairs at the last steps. This drama is good overall and the acting is amazing but the messy script in the last third brings the whole thing down.

What I liked:
***The performances. I think all of the actors gave really good performances for their characters. The main leads were great, and I especially liked Kang Seung-Ho who portrayed the grandson of the late Madam Joo.
***The soundtrack. It's nice, not overly noticeable though. I loved the intro song.
***The basic premise. If I overlook the messy details of the drama the fundamental plot is pretty interesting.
***The characters. Except for the villain and both second leads because of the flawed writing.


What I didn't like:
***Messy script/characterization in the last third of the drama.
(1.) It was an interesting decision to reveal Noh Suk Min as the main villain in the 9th episode just like that. We get to see a nice compilation of him doing his villainous deeds, and then a face reveal. Just like that, on a pretty silver platter and everything. Do the writers consider the viewers to be so dumb to not figure out who was responsible for everything? Why can't we piece everything together with the main leads? It would have been so much more interesting if we got to 'investigate' with them together. Also, Suk Min has the audacity to cry when his son and eventual victim tragically passes away due to how Suk Min was treating him? As of episode 12, we didn't get to see a close bond between the two of them to believe Suk Min's tears if they were genuine. If the tears are fake, he is not portrayed as a good actor/two-faced manipulator who has a curated persona shown to the public; he is shown as a cold and cruel person so it would be uncharacteristic to fake the tears. Whichever option doesn't make sense of the tears anyway. To me, it translates as bad writing.
(2.) The technical decision to make a whole separate episode for Gu-Won's past life instead of delivering the same information in a more elegant way. Maybe giving him wisps of dreams of how in his past life he fell in love and was made into a demon. He could have had a separate arc of finding out/trying to forget his past life with echo-y lines and foggy visuals from his dreams (you know, how people usually remember their dreams when they wake up). Mans had a whole movie play out in his mind one night instead and became conflicted about how he could be the cause of Do-Hee's downfall. This conflict could have been delivered with better writing quality and no changes to the amount of material filmed. Also, we get to see almost the same dream sequence backstory when Do-Hee remembers her past life. I can get past the first huge dream/past life backstory exposition but repeating it again and almost shot for shot? Exhausting and boring.
(3.) We are shown that after Gu-Won loses his powers his contracts are terminated, they literally burn to ashes, it's as if the wishes were never made (the little girl gets sick again). Since he got back his powers were his contracts magically restored? Why? Is this how it works? Shouldn't he make the contracts anew, the old ones burned away? I know it's nitpicky but hey, the drama should stick to its own rules.

***Stereotypical 'evil' second leads. Why do writers still rely on the drama created by second leads to drive the main romance forward? Can people truly not write good multidimensional characters that have their own story regardless of their feelings for the unattainable main leads? Both Jin Ga-Young (the dancer) and Joo Seok-Hoon (the not-really-cousin of Do-Hee) are one-dimensional 'pathetic' characters with unrequited love for their corresponding main lead. Nearing the end of the drama they come to realize that they have no chance to win over their main lead and move on, as ALWAYS with these types of characters. Uhhh. I'm just disappointed that the writers made these unsubstantial characters to drive the main leads away from each other when the main thing that is holding the second leads together is their unrequited love, warnings of how the other main lead is bad news, longing looks with eyes full of tears taped together with a few pieces of office tape.