Idk, from the start Jinwoo is an unreliable narrator. The second chapter, compared with how he sees the truth now, doesn’t align very well either, the dialogue is not the same. He said he didn’t kill any maggot, but it seems odd that he wouldn’t have done it even once. He remembers his father as someone violent (I think it’s his father in one of the flashbacks, not Guwon), and then when the doctor says Guwon is violent, everything changes.
I think the author is trying to convince us that Guwon is really twisted, but I remember how in other manhwa about zombies (not spoilers, no title), the ML seemed like the villain and it turned out he was actually good and kind.
Also, considering everything that’s happening, it could honestly go either way, it might all be a misunderstanding, or it could be the truth, and we might all end up genuinely shocked.

Idk but i think Guwon is not the bad guy that the story wants to make us believe (︶︿︶)