It was nice :) haha interesting concept. not the best for me though lol
Story is interesting had a lot of potential but I think they didn't use the whole potential of it. Better watch it without huge expectations. It turns into a mystery/detective with a bit of comedy and a tiny bit of fantasy. At first i didn't like it because they were too fixed on korean norms of beauty and ugly. However later they do say that all the people liked the guy before too who was ugly at the time. And the girl was beautiful but a bit annoying lol. Well Park bo Yeong is not ugly at all so idk why they consider her ugly but i guess they made her a haircut that doesn't suit her well.
Anyway the concept of abyss was nice, the cameo while giving out the abyss was also nice haha. idk why they call them aliens. They could have made the whole story much better with that concept but they failed to do it. As a mystery it wasn't bad. not the Best, but not the Worst either. They could have explained it more, much more... but they left everything unexplained.
the side character couple was cute. i liked that detective-mido couple the most haha.
i didn't like that they made the ending like that so i skipped most of it. But still it was happy ending so all good. wish they could explain more about the homeless person and what happened during the gap. it felt rushed in that way. or rather... felt like they had nothing to say so they made se yeon fall asleep in the middle lol
actually i skipped a lot of scenes as they were all lovely bubbly when there is a killer walking around. lol

What i liked:
- ahn hyo seob (but i think he is still too green for a lead)
- a hilarious scenes when abyss was with killer (they could have made it even funnier, but i think i just thought all the funny stuff to myself that's why found it hilarious)
- Male Lead Cha Min's mother! lol (would have thought she is that cliche mean rich mother but they made all those things very funny lol she was great, i loved when she said "bring Food!!!")

What i didn't like:
- Plot (which i liked it it was not made well, i think the writers themselves didnt get how to use it)
- Acting (well idk... i dint like it much)
- Too much romance in the later part of the drama which should have been intense
- Ending (it was a happy ending!!! but it had many things not explained, i'd say VERY not explained. but kinda a DOTS like ending again)
- Beauty/Ugly norms lol

Overall:

I can't say i liked this drama, but i can't say i hated it either. I'd say you can try it to see for yourself, because I didn't like it mostly cause i like different genres.... well i do like mystery the most, but for me this was more romance than mystery. So it was ok, not bad, but not very good for me.