Edit: like sorry if some of you clearly don't understand but yall expect him to be happy little sunshine after how he was basically tortured by Chi-Hwan's bond to him (in more ways then one), only because he was trying to save him and it got twisted? I'm not saying that it gives him right to kill someone or whatever but like you could've at least understood that he has a right to be sour after all. (But as I said before, it doesn't mean he can kill whoever he wants)

Everyone is hating on Joohyun but he still had to pay for basically trying to save Chi-hwan. He basically was getting r@ped by some asshole, then regreted not saving others (which he really did wrong so of course it's expected of him to regret it) but maybe if Chi-hwan knew the whole truth, it might have been different. So of course if he had to suffer all those years (centuries) in pain from both the bond and regret, he's gonna turn sorrow and bad. Like you can't expect him to shrug it off and be like a little happy sunshine.