Bunnaguri Sensei

Alright, it's time for class! Unleash your fists and shake up this school that has become a microcosm of modern Japan!! Manga artist Koichi Noguchi visits a high school to give a lecture. His words deeply move the students in the audience. Matsuyama, in particular, is struck by his words, drops out of high school, travels the world, and ultimately chooses to become a teacher. His new assignment is at a rough high school where every student is a delinquent. The unconventional new teacher, Matsuyama, takes on the school with nothing but his own strength!

(Source: Shueisha, translated)