Leon has to duel his shitty dad this week, but he holds his own, as he’s no longer a whiny brat consumed by anger and revenge. He wants to protect people, which is why he just can’t understand why his dad is protecting Mendoza, who has only ever preyed on the weak to increase his own power.
Herman isn’t saying nothin’, he seems more concerned with whether Leon can actually stay with him in a fight. He tries to push Leon’s buttons, but Leon hangs in there. Their fight moves to the roof of the palace, where Garm in bird form helpfully flutters over them, providing exposition. Basically, the body that governs Makai Knights and Alchemists has decided to let Mendoza release that giant legendary horror after all, since it will eat a great many other horrors, and likely destroy an in-over-his-head Mendoza along with them.
It’s a sacrifice a few to save many plan, the kind of “tough decisions” Herman says Makai Knights must make. But Leon isn’t having it. He dons his armor and presses his attack (the two wisely travel far from the city to avoid too much collateral damage). He won’t let Garm’s kind sacrifice Santa Bard, a city full of people he and his brother have sworn to protect. He won’t let one person be killed to save another. It’s arguably an even tougher stance than that of his dad, who, at least on the surface, seems to be hiding behind his orders.
Leon’s frustration with his dad’s position is made clearer in a flashback when the two were traveling from town to town, with Herman taking out local horrors and training Leon, whose present belief that every single person must be protected at the cost of a knights life, was instilled in him by his dad, after Leon tried to save him.
But his dad also makes it clear that he and Leon are only brief participants in a war that will never end. The swords they drop when they fall will be picked up with others.
In other words, there’s a long game here, and mortal knights cannot expect to save everyone and everything in their lifetimes. There are hard choices and compromises to be made that might clash with their otherwise rigid ideals, like capitalizing on the opportunity to destroy a vast number of horrors by letting Mendoza do what he wants.
Leon can’t accept the sacrifice of a few now to save many later. Neither can Alphonso, the leader of the people in the epicenter of Mendoza’s plot. Ema also seems to have the brothers’ backs. But what can they do against the might of every other Makai Knight and Alchemist who has fallen in line? Evacuating the city and killing Mendoza would be a start.