According to followers of this manga series…
It’s a fantasy story about two best friends in mid-evil times where one leads an army of warriors and the other is his greatest Captain.
The leader at a certain point loses everything he values and makes a deal with supernatural entities to gain it all back by sacrificing something of value to him. He chooses to sacrifice his army of followers including his best friend. Who are all marked by the entities with the brand of sacrifice.
https://m.youtube.com/watch?v=XcFbh93tLxU