I don't really understand all these politics. As a holy knight he has the authority to simply kill the step-mother, the earl, and the fiance on the grounds of righteous cause then head to the priest to prove who he is.
If you knew your sister was an idiot why wouldn't you leave her at home
Also why couldn't he have just launched a giant fucking rock at the castle from outside the barrier and obliterated it
manga logic 10/10