As the title says, I think this drama is really catching! More you watch and more you want to see. In my case I've a weird reaction, because I'm watching other dramas right now, that I think are "better", but I don't wait for them as for this one. Happiness has that "I don't know what" that makes you stay with your eyes glued on the screen. But don't get me wrong, it's a really good drama, the acting is really really good I think that what works really good it's the dynamic of the characters.
I don't find the story really original, but it works good, as I said in a comment I think who wrote this drama started from the idea of covid, because when I watch this drama I cannot not think it's what happened to us, just amplified to supernatural to make a tv product. And this is in my opinion what's make us love this drama, it's like they're joking us, a sad joke. The lockdown, people going crazy, people not caring, selfishness, stupidity and more..
Anyway I really like the leads and their chemestry, they work really good on screen, their characters compese eachother pretty well giving us balance. As I said the strong point in my opinion is how all the people interact with eachother once they're forced to lockdown together, the characters are so differents, and those two are practically the unwanted guardians of them, I still have to figure out some of them, because obviously, some are really shady!!
Putting all together this is a really good drama, this is just my opinion, but I really recommend this one! :)