I am torn, the story begins as the synopsis indicates and that a young man - Yoon Jong‑woo - will live in a residence where his neighbors are more than suspicious.

The problem is that there are only 10 episodes, and they could have made more use of them.
We practically have to wait for episode 3 to have a first interaction between our two protagonists, and it is neither memorable nor long. The build-up is slow, not much happens except the fact that we know from episode 1 what kind of people are his neighbors, it's a shame that it's not a surprise or a revelation for later, it would have been nice for the audience to wonder who is who.
So basically, until episode 7, the plot is slow - which is not a problem in other series - but here the interactions between our two characters are rare, there are no surprises and major revelations. Seems more like it's the build-up to why Yoon Jong‑woo freaks out and gets violent.
I agree with a review that says the show is all about insanity. The story isn't that amazing and it's really focused on our main protagonist going from normal young man to giving a free ride to his violence, the series has build-up only that.
I would have liked more, more between our characters who have a certain chemistry, that we understand more the motives of these characters since they are not mysterious.
All we have are two twins who giggle and are murderous, an equally murderous perv, the manager who seems just as crazy, and Seo Moon‑jo the creepy dentist. It feels more like these characters are here for the grand finale and when people will inevitably have to die.

I would say otherwise that the atmosphere and the tones of the series are well created, it's more or less scary, dark and horrifying. The overall production is good - but there are plot holes - and the actors, all without exception, fit into their roles perfectly, but none of the characters marked me personally.
Like I said already, the two protagonists interact very little, and suddenly Seo Moon‑jo decides that Yoon Jong‑woo is very special to him, without there being a tangible relationship between the two, except Seo Moon‑jo being creepy since the beginning and stalking Yoon Jong‑woo.
It's really the relationship that pops up, out of the blue, which is why I wish I had more episodes or else had them interact earlier so it doesn't seem so sudden.

The very end - the last ten minutes - is really the exciting part of the show, that ending is open ended, our character is inevitably changed, and there's a last minute twist, which leaves us with a possibility for a season 2 - even if I doubt it - and the return of a character.

But it's a nice crime series overall, it's not the scariest of the lot, nor the best scripted, but it's nice for those who like the genre, not a lot of mysteries though, it's more into the impact of scenes that are made to be scary and made us feel for Yoon Jong‑woo, but hey without suspense, it's hard to keep an interest.
The characters play their roles well even if I would have hoped for more, even coming from our two protagonists whose performance is good but nothing more.