the biforcation blade

Inside was a sword and a note.

Stefany was amazed. Who the hell sends swords? The note read "bifurcation blade." This sword is capable of cutting anything in half.

Stefany considered the comment absurd. A sword that could cut anything? She bet it didn't even have a sharp edge.

She ran her finger over the sword... cutting off her finger and panicking.

Stefany: Oh, my god! It really is a real sword!

But a few moments later, it was as if nothing had happened. Her hand was completely normal, no fingers missing. She hadn't felt any pain or bleeding, as if everything that had just happened was just a hallucination.

???: aaaaahhhhhhhh!

Hearing the scream, Stefany turned around and sat on the ground. There was a woman identical to her, pointing at her and screaming.

The bifurcation blade had cut her in two perfect (whole) halves.

(I'm drawing inspiration from the story "The Bifurcating Blade" from the now-defunct Blueversusred forum, which featured tales of incestuous twins and clones.)