Minor spoilers
They go to kill a mage who is killing tens if not hundreds of people and turning them into undead ok noble goal stop the serial murderer but then the dumbest thing i have seen in a manga happens the characters look at her research about undead while burning it and think "What is justice?" Like bro she murdered people for RESEARCH massacred a whole village and you are like hmm what would my father do in her situation is this really justice? Tf you mean is it justice you killed a necromancer who murdered for her own gain you were in the right.
She gets 1 chapter of background which for me made me hate her even more at least we have a reason why she did it (Spoiler it's a decision she made as a goddamn 8 year old and kept to her whole life) Her pet died and she didn't want a replacement so she murdered people to find a way to bring it back. That dosn't justify shit she bad get on with it the justice was right.