I think this is why people have "dropped" it.

Those that are getting bored will probably come back when the story is completed, at least to get some answers. But here's the deal. When it comes to a story built on suspense like this one, especially concerning whether the main characters die in the end or escape justice, you kind of have to make a choice. Either things are urgent in the real world (like when these two were raising suspicion with the local police) and we understand when we're seeing a delusion of the main characters, OR the "real" world IS the delusion and we get hints of that throughout in a slow burn kind of way. You can mix the two sometimes, but this story started off as Natural Born Killers not Memento. People seem to be fabricating tension with theories about how some of the characters might be dead, and I don't think that's the case. I think the story just hit a lag because Seungbae is the only threat to Bum and Sangwoo and he's struggling to eat and shave right now.

A quick caveat for why I don't think anyone is dead:

We have three protagonists, so we can't write everything off as a delusion. Seungbae isn't in Bum's imagination because we see his POV separate from the other two. Same with Sangwoo. He has his own memories and moments away from Bum. Bum is a given since this story started off with him as the protagonist. They're all real and alive is what the story seems to be saying. Other people have seen all three of these characters outside of the house or each other's presence too. We're not meant to take their delusions that far because we're usually shown the truth after we've been toyed with (like Bum waking up from a dream rather than getting up from the bed, plus the creepy ride and clown images). So we have a baseline reality that we've been set up to trust. Nothing has been set up to suggest for example that Sangwoo is dead and a projection of Bum anymore than Bum is a projection of Sangwoo's. The uncle too, is likely dead since we can usually trust Bum's sense of touch in this story.

So now to the lag. Seungbae is a good character who is being misused. We're still waiting for Seungbae to get back on his feet and pursue Sangwoo. Right now he's ALSO going crazy. I get having doubts and hitting a slump, but he's completely out of commission right now, at the same time that Sangwoo and Bum are going through this weird lull themselves (seriously why is Sangwoo hiding from Bum instead of watching his handiwork? Where is he?). We have delusional guy #3 up against two other delusional guys -- who in between having sex, going on outings, and killing the occasional person haven't got a plan or anything to really do outside of that. No goals or motivations. Bum isn't exactly being held captive anymore. Sangwoo isn't thinking he should kill Bum, or pack up and move now that the detective knows who is. They don't have any urgency to go to work or school, no family and friends who could stumble onto the truth. They're in limbo and now the detective is in limbo too. So we're in limbo.

With stories like this you have to believe the author has control and they know what they're doing even if no one else does. But I think a lot of people are getting the vibe that the author isn't as in control as she was in the beginning. Either this story was stretched out to keep drawing in readership, or certain plot points weren't planned out enough that the serial nature of the story could still work even when the drama slowed down a bit. What we're seeing isn't exactly character development to take the place of the suspense, which would make sense at this juncture. We're seeing characters we already know doing things they've already done and the only question is "when will they stop doing that and actually engage with each other, leading to some sort of climax?"

I don't necessarily doubt there's an endgame in mind, but changes happen. And if the author made any changes along the way the story seems to be struggling for them. If they didn't and this was always the plan, the execution has hit a bit of a snag in my opinion. All three characters are forming a bit of a straight line when they used to form a triangle and we never quite knew who was going to team up and who was going to come out on top. That's why I don't think people who have lost interest are dumb, not all of them. I think some maybe don't even know why they feel the way they do consciously, or can't articulate it beyond wanting more blood and sex. But for me, someone who likes the story, likes slow burn character development, as well as the violence, it seems like I'm not waiting for the next chapter so much as 4 or 5 chapters from now when I may get some answers as to what these aimless characters are going to do. Even Bum when it comes to his uncle didn't DO anything. He watched. He ran. His very dreams are passive things in which things happen to him. When the characters start doing something different readership will probably come back.