Your Head's Fallen Off Again

Everyone knows slaying monsters make you level up. But me? I AM the monster... I'm the only zombie on Earth who can survive having my head fall off. In order to stay alive, I've hidden my identity, laid low, and pretended to be just another corpse. Also... I couldn't stop worrying about my frail ex-girlfriend—so I decided to protect her from the shadows. But, who knew she’d turn into a badass zombie-slayer? And now she’s found me?! I flee, she hunts. Our fates are like an entangled mess. And KA-BOOM! The whole world is doomed! Alright then, no more hiding. The truth is... I'm the vaccine.