You're a human that has fallen into Mt. Ebott on the year where all humans dress as monsters...Halloween. So how will the monsters know if you're a human or not?
You died. Again. But, when you woke up... You were back at the beginning. You didn't reset... but something was off. Flowey seemed skittish, frightened even. He was KIND. The people you knew, you once held dear... CHANGED. The entire underground was different... Dark. Nobody seemed to recognize you, but a part of them...