Apocalypse no Toride (アポカリプスの砦) is manga written by Yuu Kuraishi and illustrated by Kazu Inabe. It was serialized in Shounen Rival from September 3, 2011 to August 4, 2015.
What can you do when you're mistakenly accused for murder? Nothing. You just go to prison. Lucky you; your inmates are some of the biggest cutthroats in the prison. Seriously, you are lucky. Especially when zombies attack.