Sento Zonbi jogakuin

There are zombies everywhere. They roam the land. Vast area, lands, cultures, cities and towns have been lost to zombies. Seven girls live in this world. They live in a school protected from zombies by a fence. The girls study the zombies including how to fight them, escape from them and to defeat them. A zombie bites one of the girls in a class one day. The seven suspect something is wrong with the school.