beta
It's well-accepted in the bl-universe that a tragic backstory should never justify or excuse a ML's poor treatment/behavior towards the MC. At some point, we all become adults, have to own up to our sh*t, and can no longer use the excuse 'but my parents sucked'. That's why at the end of the day, JJK doesn't get a pass for his poor treatment of KD. Don't get me wrong, I don't think JJK needed to treat KD like royalty, or with affection, or even very much care. At the end of the day, JJK wanted a transactional relationship(prior to his match). His biggest flaw was acting abusive and taking his aggression out on Kim Dan when it was uncalled for, and treating him like a tool rather than a professional partner.
With that said, I still do enjoy this backstory because it adds layers to JJK's character. We see that he's a self-made man, and someone with a determined drive since birth. We see another reason why he moved KD out of that dangerous apartment so quickly, and why he's fond of old ppl. We also see why he's so determined to train and win. For him, fighting was both an escape and his lifeline, his key to escaping the hellhole he was born in. The backstory illustrates a bit why he is the way he is. It doesnt, isnt supposed to, nor should it justify his treatment of Kim Dan. It only explains why, but reasons and justification do not always go hand in hand.
So the current status of the MC's is this: JJK needs to learn self-worth outside of winning matches(note the nightmare he had), and to carry more respect and self control towards others. Kim Dan has abandonment issues, and needs to learn to accept loss and change(bye grammy).