99 Boss is a Manga/Manhwa/Manhua in (English/Raw) language, Action series, english chapters have been translated and you can read them here.
The protagonist, Na Seon-wook, was born with the heart of a tiger. He was a troublemaker, but at the request of his parents, he hid his strength and transferred to Gukyang High School, a school located in a remote area that he thought would be quiet. However, it was a place where various old-fashioned cultures and dangerous people gathered. Seon-wook, who wanted to graduate quietly, eventually he couldn’t help but feel his hot blood and began educating them!