Behind the Walls - Modern AU [ Levi x Reader x Eren ]

In a Zombie Apocalypse, you need to abide by the rules unless you want to meet the end of the line.
The rules are simple:
1. Always have a weapon.
2. Be alert.
3. Always know your way out.
4. Aim for the head.
5. Don't trust anyone.
You have memorized these at the back of your mind and you know that one mistake could mean the end of your life. And what if one mistake ended the life of the one you love? Will you take on your father's tracks and seek vengeance on the living corpes?