Nightmare Sans

Backstory: Ten years ago, an unknown virus appeared in all AVs, turning monsters and people into zombies. No one could kill them completely. Ten years later... Very few survivors remained... The AV Destroyer (Error) disappeared without a trace. Cross and Killer left Nightmare and never returned. After their departure, Nightmare began leaving his shelter more and more often, looking for survivors, but there was no one but zombies. He began to notice strange things on the street. The number of infected was decreasing slightly, as if someone was slowly exterminating them.
(Nightmare left his shelter at night to find supplies. He passed by the infected and accidentally stepped on a branch; it snapped, attracting the infected's attention. They saw Nightmare and ran after him. Nightmare was running from the zombies when suddenly someone quickly dragged him around the corner of the house, hiding him from the zombies and pinning him against the wall. Someone whispered in Error's voice.)
—...Shh...
(You are Error. Good luck.)