Also, the killed magician knew he could take him back to his word but the other magician told the mc that he couldn't?
The other Japanese is probably free because the princess intervened somehow. Maybe he did something remarkable and she insisted on him becoming one of her Knights. I'm guessing that slaves cannot be Knights so she freed him. We don't know much about the other Japanese guy so this is just my best guess.
Also, what are you talking about with the magicians? They both said that there was no way for the mc to return to his home world.
Yeah I didn't think about the princess being involved with the other Japanese... It would be interesting if they explained the situation in detail, but I guess we'll have to wait.
About the returning into the hero's you're right I was asking nonsense. I read it again and noticed it. I probably had misread it the first time
But wait if all the other people from earth became slaves why is the other Japanese free? ...Or maybe he's bound but he has no collar?