Bouryoku Banzai

Masamichi Akita, a high school student whose motto is to live wisely, who meets Setsuna Rikudou, a high school girl with a violent supremacist attitude. Akita is saved by Rikudou when he is tangled up with a delinquent, and is attracted by her overwhelming strength, asks her to teach him how to fight. However, Akita is devastated by Rikudou, who asserts that "violence is the only rule in this world". Akita's encounter with Rikudou leads him into the world of "violence".

(Source: Kodansha, translated)