I understand that I know he has major issues & I'm sure if he were to explode someone could die or be seriously hurt but the same could go for Minji too. ijs based on from what I've read till this point Minji seems more demon-like. No-one in this story is a good person they're all using each other for their own personal gain. MC for money & comfort, Minji for whatever plan he got for the outside, Heonjae for companionship & they all have major issues that need to be dealt with. But ultimately Minji is the Captain of the ship & everything we have seen him do has not equal up to what Heonjae has done so far. So it's a little confusing to me.I guess he being quiet & timid is scary.
The fact that the other people in prison with them seem to be more afraid off H than they do M I think is what eludes to him being the most shockingly scary, plus like you said his timidity and shyness. The Devil you know is less scary than the one who doesn't seem demonic at all. You have no choice but to ask yourself “what are they hiding”
I'm not sure how Heonjae got turned into the villain of the story when he hasn't really did anything.He said one thing about wanting to harm the MC during sex but didn't act on it and he has been deemed as the devil himself. He has been nice to the MC the whole entire time. He just needs better guidance and communication. Minji is still the worse out of the two for me. I do wish Heonjae would leave the MC alone completely. It makes me sad Everytime I see him treat Heonjae like shit on the bottom of his shoe and treat Minji like a friend. Cause how you scared of the guy who is scared to talk but not the one who be knocking yo head in between the washer and dryer.