Sweet. "rivals" who are total pricks and quite literally want to watch the world burn. I hate them already.
Seriously though, I also probably should've expected this sort of development. Our MC here actually could have easily been one of "them." Instead of feeling complete fear and gradual loss of emotion for the black company he worked with. It could have easily been anger, and vengeance. Granted, our MC is of good-nature, so his bucket list is also of good heart.
As the quick flashback shows for the enemy though, they are anything but. They host a strong sadistic sense and are going to act out all their desires to give the grandest middle finger to any "society" that exists, including this small, happy village WILLING TO ACCEPT THEM.
My prediction: They succeed. Burn everything. Watch as the "normies" die, and MC feels incredible anger. His "heart of gold" however will prevent him from actually wanting to kill him. "Bad bois" get away, expressing their desire to search and destroy, with MC team trying to help out any survivors they can hopefully find.
But good GOD I hate it when the author puts this type of "cruel villain" in the series. I'm not saying it's a poor writing strategy because i'm not a critic, but that I just have an unanimous hate for them, like Meine from Tate no Yuusha. They're designed to be completely hated with little to zero room for any form of sympathy so when they get their "just desserts" they all but deserve it. I'm fine with one track personalities, but I'd at least want a personality that's not springing negative emotions. I just. WHY.
tl;dr: Characters written to be complete assholes are really godamn annoying and I wish they didn't exist, even though they serve a functional role in the overall plot and character growth of the good guys.