Oh shit, I just noticed the incantations the guy is saying make sense. He says, "Nvohke" (Invoke) followed by "Anlokhe und Anfjolde" (Unlock and unfold) to supposedly open the metal book. That just adds to the weirdness of this story so far. There is clearly something strange about this whole thing and it is playing with the Isekai tropes. Like I said, I'm actually eagerly looking forward to the next chapter. Also, I think those spearmen were positioned behind each of those summoned for a reason. Maybe to take care of any issues if they get out of control or something even more sinister.