Immortal Body

In a world that is very identical to earth, a catastrophic event happened. Almost half of the population was swept by this event, bathing the land of this world red for a while, but not quite as some of the human beings in this world already new of this event was inevitable. They have prepared their forces and waited for the event to happen before launching a counterattack and trying to save as many cities as possible, from the sharp claws of the invaders.

Our protagonist was just an "ordinary" student at one of the prestigious schools of this world when the cataclysm happened.