@Ian
Spoiler!
Park Hayool? Well he become one of the villain in a much much later chapters. Yoojin lost contact with him, and when they meet again he's already awaken with a quite powerfull skill. He has obsession for yoojin since he save him, and later he also has bad experince with S-rank hunters, so that's why he really hate S-rank hunters or higher. He's not a villain that want to bring "harm" to yoojin, instead he bring harms to others close to yoojin because he's obsessed with yoojin and want to have him for himself. He's a quite important character in the future chapters
V