Manga by author Interstellar entertainment ( 星际互娱 )

Da Lubei, the older brother who rules over the entire district, suddenly declares that he's going to become a good student! He carries the "Student Rulebook" around every day like a Bible, swearing not to ever fight again. When the leader of an opposing gang comes to seek trouble, Lubei couldn't bear it and finally... goes to tell the teacher?!