Generation X - the origin of Yuji Amanda

An action, drama, with a pinch of romance story, where it takes place in a world where mosnstrous creatures called akuma's roamed over the surface of the earth, infecting humans, turning them into one of them, and humans lived inside city walls to survive, where a new generation of humans gained supernatural powers/abilities to survive and fight against these creatures.

Yuji, the main character, was close friends with the strongest person and most famous female student on their school, but Yuji was being discriminated for having nothing but a strong immune system for an ability.

When the time of tragedy comes, how will a person with just a strong immune system survive?