This had potential to be a really good and different type of kdrama. Sci-fi, romance, and mystery could've really worked together if there weren't too many convenient chances of characters just meeting up or things happening out of nowhere and without proper explanations/reasoning.

There isn't much explanation of why the "aliens" left that device to ML at least not in the first 3 episodes . Don't they have rules in their own world? What if someone asks for their device when they get home? And why does the device works for other people too when it was originally given to the ML. I know I'm reaching out here but the writers should know that you can't just introduce sci-fi stuff without any proper explanations.

Too many convenient coincidences for the killer took me out of this story. The story idea is good, romance part is also good but these coincidences and plot armors were too much for me to keep watching it.