I didn't dislike this drama, really, I didn't. I actually found the sweet romance to be adorable to watch, but switching from sweet cute romantic comedy to dark murdering killer scenes was just too much for me to comfortably enjoy on my couch in the evening...And honestly, the bad guy was just frickin creepy...
When the scenes switched to the bad guy, I got such Criminal Minds vibes (that spooky thriller bad omen vibes) that I'd be too spooked to sleep comfortably. I'm a pretty big wimp though, so maybe my interpretation of how spooky and scary the bad guy was is just me...
BUT, something else I found jarring was how the romantic comedy was very slap-stick in nature, and then it would switch to the bad guy and it was very dark and scary....the abrupt switching between both extremes of those genre's just didn't smoothly blend and transition to be in one drama. I think if the bad guy scenes were less creepy and dark, I'd find the drama less unbalanced.
Overall, I did like the romantic comedy aspects, but inevitably, I dropped this drama because the scary scenes were just too outside my comfort zones for me to enjoy this drama in its entirety. You might find this drama fitting to your own preferences though, so I don't think it'd hurt to try starting and see if it's something you enjoy.