AMI Kenchirou (looks like a girl) was stabbed and killed.

However, he woke up not in a morgue or in a hospital but under a bridge. With no pulse and a cold body, he was indeed dead. As he was wondering what to do two girls appeared in front of him, Katarina and Nora. Katarina is a self proclaimed genius scientist studying zombies and the living dead like Nora and probably Kenchirou. Kenichirou decides to help Katarina and Nora to gather the living dead, the story of the strange community begins.

(Source: Baka-Updates)