Apocalypse Zero

Apocalypse Zero (覚悟のススメ, Kakugo no Susume) is a manga written and illustrated by Yamaguchi Takayuki.

Plot
In the near future, a series of devastating earthquakes have left in Earth's civilization in ruins. In one part of Neo-Tokyo is Gyakujuji High School, where paranoid students and a corrupt principal try to maintain order amidst the mutants that roam the area. Quiet but self-assured new student Kakugo Hagakure wins new friends when he saves class sweetheart Horie from a horrific woman-beast that attacks the students. Equipped with an impenetrable suit of armor and martial arts skills, Kakugo is a true human weapon, and as a power-crazed overlord sends out more monsters to terrorize Neo-Tokyo, only Kakugo can stop the chaos.