There is a female classmate in the class who is often bullied. Today, as usual, she was called to the corner early in the morning and beaten and kicked by other classmates. However, we take these things as a matter of course, but no one is willing to help. Just when we thought it was about to end, several people who were bullying the female classmates suddenly let out miserable screams and fell backwards with bright red blood spurting from their necks. The nightmare began from this day. The few "lucky ones" who saved their lives fled to the sewers to live in order to survive. I thought I would stay here until death, but I never expected that I would be dragged into an event even more dangerous than this by a strange man.