When the mysterious asteroid "Hakon" collided with Earth, the world was instantly transformed into a hellish apocalyptic wasteland overrun by zombies and mutant monsters. In this brutal new era, Shu Hirai met a tragic end—not torn apart by monsters, but stabbed in the back by his own comrades.

Swearing a bloodthirsty vengeance with his dying breath, Shu suddenly awakens in the past, mere moments before the zombie pandemic erupts. But he didn't return empty-handed; he now possesses a supernatural "Skill System."

The old Shu was a pathetic loser who cowered before his bullies. The regressed Shu is a battle-hardened avenger radiating immense bloodlust. Armed with the overwhelming combat experience and cold, calculated judgment he forged in the apocalypse, Shu delivers merciless retribution to his bullies and future betrayers. Wielding his newly evolved "Skill System," Shu will crush anyone in his way to become the apex survivor of the ruined world, vowing to protect the true comrades who died for him in his past life!