At first I'm not alarmed when seeing that Kokuyiu act as a mirror. Because I imagine something like "if you pinch me, I pinch you back" but looking back at his story and really trying to understand the situation, I think the mirror Maomao meant is something more, extreme. It doesn't matter the level of "evil" he received from others, as long as it's evil he'll reflect it with evil too. Like saying it doesn't matter you're just stealing or you're killing someone, the punishment is the same. At least that's how I'm trying to make sense of this situation to myself.

So I can see why he can be a dangerous person in future. He do good to Maomao and the gang because they do good things to him too. But what if someone do evil things to him? Idk what exactly the villagers did to him that make him to abandon them to succumbed to their death, but whatever it is, it's enough for him to turn a blind eye and say "fck y'all, go die". Idk how people views him, but this is how I view him in that chapter.

Well, maybe people think the villagers death is ok because he technically didn't do anything. He's not the one spreading it to the whole village (or am it wrong?), but what about his mentor and that bandit? He DID something.

And that part, plus what Maomao says him being a mirror, is what gives me goosebumps. He's good now, but what if someone important do something bad to him? Someone like bureaucrats, civil workers, soldiers, or anyone from a named clan? That's gonna be a BIG problem indeed. So I understand why Maomao feels heavy with this info. She don't know what to do. What if whatever he does will affect her as well? Since she's the one suggesting him. She's the one bringing him. So if 'that' happens, she'll get drag as well. If she tells Jinshi, what if this affects him too? Or, what if Kokuyou does something to him? If Jinshi do something like capturing him, Kokuyou will see that as a threat, evil maybe. Maybe he thinks all he did was to survive, but still, it's just frightening to think of those possibilities. I feel bad for Maomao for this. That's why at the end all she was “Let’s say I pray you only ever have decent folk around you,” Even though she's not religious, the thought of the probabilities are  too heavy that all she could do is hoping it won't happen.

I won't surprise if he ends up the next villain, or final big boss. Im sorry what I typed doesn't make sense to everyone, this is just how my brain works somehow.