As time went by, the boy's reputation grew. Countless adventurers had perished under his hand. He had also grown a lot in power. He had gotten the title of "Demon Lord" which was only given to those with a complete understanding of the demonic ways. It was a title that made every demon look at him with admiration and respect, therefore, he was able to contract any demon in existence with ease. And so that is what he did.
The boy then lived peacefully in a valley that had been named "Hell's Gate" due to the number of demons that lived there. The boy, who was now a young man, was the only human being in the entire valley. There had been countless times that the rulers went after him, the valley had been under attack by hundreds of thousands of adventurers but they were unable to subdue the demons. These demons had complete loyalty towards the young man. He had given them a home outside of Hell.