Hmmm, what if there are people from that other world, or another returnee. Or else earth has some rudimentary magic, which is why the description says he is training them?
they take you out into the woods to fucking kill you and all you do is give them a light beating and then heal them? wtf? is being a complete pussy in your DNA or something?
So you find somebody willing to kidnap and kill other people out of fun and spite and as a hero think you should not kill them? Do you feel they'll just stop being murderous garbage altogether because they're not attacking you? Quite a hero. . .