I'm not really a sci-fi fan, so I wasn't expecting much when I started this drama, but I was hooked from the start.
The drama moves smoothly, avoiding many plot holes that most of these dramas fall in, you'd expect you found one and it turns out to be part of the plan or an unexpected plot twist.
I've known Siyoon first from Psychopaths' Diary, so it took me the first 4 episodes to not laugh everytime he has a serious expression, but he's a good actor and did well in this role.
The only part I didn't like much was how rushed the ending felt. They left unexplained bits that don't affect the overall plot, but still made the last 20 minutes feel like the director was saying "You get the idea now, you'll figure it out". Which isn't so bad, it might have dragged a bit otherwise, so all in all, it's one of the best shows with that idea.
