The zombies couldn't break through, but the humans couldn't push them back either.
Zombies feel no pain or fatigue, but people do. And while physical exhaustion could be managed, the mental fatigue was even more crushing.
The mutated plants didn't feel fatigue, but their attacks were limited; there weren't enough to hit every single zombie. Moreover, zombies at Level 4 and above required the combined effort of humans to be defeated.
There were just too many zombies!
Even when they killed a large horde of zombies, another would immediately take its place. Most ordinary people had given up fighting to focus on harvesting Spirit Cores instead. Many minors had also joined the effort, digging for Spirit Cores in the corners of the battlefield where they were vulnerable to surprise zombie attacks.
In the face of crisis, the young boys and girls were forced to grow up faster than their age would suggest.
