@evarcrazy89 yup, they didn't really say that the charm grew his conscience
because they were too busy continuously implying it multiple times in quite a few chapters
he and his blood in general are brilliant martial artists but are also easily swayed into becoming bloodthirsty killing machines who kill their emotions to become even more efficient fighters
they literally stated that his father understood that and so he didn't dispel the charm
half of the mentions we have of mc before the initial charm are about him doing messed up stuff or are implications of him doing messed up stuff, and presumably not in self defense but just from apathy about human life
the dad understood that experiencing love forcefully would change him as a person, and now it lasts even when not talking about the girl
hes learnt lasting empathy and concern for other people and his relationships