Adventurer Super Justice

Jon traveled to the era of disaster when demons ravaged the continent, and what came with him was Goldfinger, who could become stronger as long as he did good deeds. "Why does killing demons count as a good thing?!" "In that case..." [You killed the demon generals and helped the civilians escape from demon slavery. Your righteous deeds are worthy of praise. You have understood forbidden magic, ancient secrets, advanced swordsmanship, and super talents...] Jon stared at the black tide-like demon army in the distance: "The country is easy to change, and the nature is hard to change. The demons must not be trusted!" "I'm too lazy to reason with you, you don't deserve to listen!" "You were a demon before. One day you were a demon, and you will be a demon all your life. I won't let you go if you beg me!" "Demons, I will definitely destroy all the demons. I am the only one who is undefeated!" [Demon-killing tribe + a Western fantasy adventure with a bit of Japanese style]