Aiming for Maximal Level in a Post-apocalyptic World

Five years into the apocalypse, Earth had become a living hell. Chen Shao’s beloved sister was killed by demonic beasts, and he was powerless to protect her. However, when he woke up again, he found himself reborn back to the time before the apocalypse and even gained supernatural abilities! A new system appeared, telling him the way to save his sister. But there was a condition: he must continuously level up to prevent the apocalypse