There are four versions of this: 2014 Korean, 2017 Filipino, 2019 Thai and 2022 Japanese. I’m reviewing the original 2014 Korean version (which, based on the remakes alone, was very popular).

Besides being a SciFi drama, it reflects the cult of celebrity and its impact on the person behind the persona. Oh, and there is a ruthless killer. And, oh, there is a 404+ old alien waiting on earth to go home. The premise is SciFi and sets up the drama which held my attention for 9 episodes but the comedy became so ridiculous that it spoiled the pace for me and the focus on nothing but unrequited love spoiled the chemistry for the next 5 episodes. I definitely had issues with the pace, and the lack of consistently quality writing but there were episodes that were undeniably 8s.
Overall, the acting was spot on, the characters interesting and the premise fun. I give the series a high 7 (enjoyable) out of 10.