The apocalypse broke out, and all members of 313 were trapped in the school.
Good news: There are only senior high school students and teachers in the school
Bad news: 313 is a senior in high school
On the fifth day of being trapped, 313 got angry and then decided to act recklessly.
After rushing out of the campus, human society has changed drastically. After embarking on a road that leads to nowhere, they remain the same.
(Don't hit me if you don't know how to write an introduction...)
Concept: Girls support each other, human evolution (?)