Start with a Bone Chopping Knife

Affected by the electromagnetic riots of the sun, human emotions rioted and turned into man-eating zombies. Two-thirds of the world's people have mutated, and what happened to the remaining one-third? Bai Zhi starts with a bone-chopping knife and cuts a small zombie. The little zombies are fragile and can be slashed with one knife, while the mutated creatures have hard shells and are fine, and can be slashed twice. (No supernatural powers, no Holy Mother, no entanglement.)