this yes
It hasn't come up much in the story, but there was that phenomenon that caused people to rise back up from the dead as moving corpses that were non-threatening. This scared people, but also made them think this was the means to create immortality and scientists were searching for a way to make it happen. This research abruptly was stopped because then the apocalypse happened as disaster after disaster happened.
Theory:
I think Guwon was an experiment to try to create immortality, that was released when disasters struck, which is why he is so inhumanly strong and looks like a zombie and has no memories. He would be above humanity in the food chain, like how humans are above animals. That would likely be why he's see humans as pets.
It might be possible that Jinwoo, on the verge of life and death at the beginning of the story, became something also inhuman having been affected by the phenomenon that brings the dead back to life while still keeping his sentience intact. Jinwoo also seems to have almost prophetic dreams that are warning him of a bad future. There's one before he learns the truth about Guwon and the town trials where a bunch of people in the town are dead and are blaming Jinwoo for it, including the doctor.
Guwon just thought Jinwoo was a normal human, but now maybe he's noticed something and he sees Jinwoo as being different from the rest of humanity, just like he is. Guwon has never had someone he could consider an equal.
THIS.
Yep, it's very much that Guwon might even be THE successful experiment. I put in the chance that the author could do a rug pull and having him be just weird, but honestly I find that highly unlikely as it seems to be building up to them both being something else.
Guwon doesn't seem to have any memories of ever even being human, so for him, the Teach's actions are probably confusing as he genuinely doesn't understand caring for humans as equals.
Not to mention, it's very obvious that Guwon seems him differently then he did from the start, where it seemed he was watching over a puppy he thought was cute, to suddenly realizing he might not be alone like he had always thought. It's no wonder he's endlessly infatuated with Jinwoo now instead of just humouring him like it was at the start. Nothing else matters to him anymore, just Jinwoo, it's why he would gladly kill his own hounds for him, what's a couple of dogs compared to the life of his one and only companion?
Jinwoo has no idea how far this man will go and barely comprehends that this goes much deeper than a grudge over killing (or most likely not) his father, because he doesn't know the loneliness Guwon likely struggled with. That's likely where the story might be headed, Jinwoo finding out what the other had gone through and having to come to terms that they're the same.
That he is JUST as much of a 'monster' as Guwon is. Perhaps even worse.
Guwon believes himself not to be human, it seems quite obvious he genuinely isn't, or perhaps it's all a twist and he's just crazy.
But regardless, he views the others as a different species and is, therefore, uninterested in any deeper connection. They don't think like him, they don't act like him, but he takes care of them like one big dog shelter as they can't survive without him looking after them.
Whether Teach is actually like him is the interesting part. Clearly there's more to him than even he, himself knows and I can't wait to find out.