noh's maturity comes from his teacher and family, he has a good heart but he's also rash and immature, now that he's alone and has a reason to seek power related to his family, it makes that he'd be more easily swayed by the metal ki, by nature he isn't totally mature, it's a part of him that he's built up but the metal ki is throwing away that rationality and character and bringing out that dumb thug side of him.