Kochira, Shuumatsu Teitai Iinkai.

Kotoyorozu Kotoha, a boy with an underground past as a former mafia underling, had given up on youth. However, his life changes completely after meeting certain girls. With massive guns, they fight against mysterious beings threatening to destroy humanity! This is their school life — full of chaos, action, and unexpected twists. Behind the facade of the world lies a wild and outrageous youth like no other!