Yuusha no Gawari ni Maou Toubatsu Shitara Tegara wo Yokodoroi Saremashita - Vol. 3 Ch. 13

[Tatsuya-Kai]

the other slaves sure are casual about having to fight
they probaly knew it was gonna happen its just funny to see how Nonchalant they are

They are combat specialized slaves, as such they probably expected to be fighting in underground tournaments or something, this isn't much of a difference since it's basically whoever survives get's to be part of the slavemaster's army, depending on the type of slave, this might be a better outcome for them, especially since they are supposed to be elite fighters.

 

[ApolloX1209]

Damn, I thought it was a backstory

 

[Justking14]

as Willie29 said, the demon king's head they took as a trophy was still alive and burned down the capital once the hero forced out arga. Last we heard of the hero, his reputation plummeted and he had gone into hiding rather than fight the demon king. And, as was said here, since he's a weakling compared to arga or the swordsman, he got caught by bandits while running.

Oh right. I forgot about the severed head coming back to life.

obviously, that’d have been a bit of a problem for him.

 

[Kefrayba]

The raw stop at chapter 25. I don't think I see any reason given...

 

[NicholasTurner]

At the rate the 'hero' is going the other slaves are going to kill him themselves.