The sword hadn't driven you completely insane, just mostly insane. After bringing the sword down in a wicked slice through Michelle's shoulder right shoulder, her tank top leaving you a clear shot without having to worry about whether or not the magic would work on her clothes, you watched the cut and waited for confirmation that this sword's magic was legit and that you hadn't just horribly mutilated your longtime partner. Luckily for both of you, the note had been telling the truth. Michelle's arm fell away from her body with a thud against the thickly carpeted floor, her fingers slowly and deliberately furling and unfurling as she inspected the smooth skin that stretched over her shoulder stump.
Michelle looked up at you with a more brilliant gleam in her eyes than you'd ever seen, silently shaking as and opening her mouth as if she were about to laugh. "Holy shit!" she whispered.
"I told you it would work." You said, a little smug despite what you just did being one of the dumbest gambles you've ever pulled in your entire life. "So, now that we know this is legit, would you like us to live out the first of our many deviant fantasies?"
Michelle smiled, sliding her purse down her left shoulder and setting it aside so the strap wouldn't get in the way. She knew exactly what was coming. The two of you had spent many hours describing exactly what you'd do to one another if either of you discovered Natural Body Magic to be real, an unhealthy amount of time given the sheer statistical improbability of the fantasy but time that was provably not wasted. You both knew what you wanted to try first, and as Michelle stretched her arm out to give you a clear shot, you knew that reality hadn't altered your fantasy plans. With another slash your girlfriend was left armless, her stumps ever so slightly uneven but not enough for either of you to bother correcting. Turning and sauntering over to your bed, swaying her hips in such an over the top display that it danced the line between comical and erotic, Michelle spun back around and hopped up onto your mattress, spreading her legs wide and stretching them out of you to take.
While you wanted to hack off both legs in a single strike, you knew you weren't that good and would've ended up with weird diagonal stumps. Taking a knee and propping Michelle's legs on yours one at a time, you set the blade down right along the hem of her jean shorts and allowed gravity to do the cutting. The magic had clearly done something to empower this weapon's edge, for it glided through Michelle's flesh and bone with the exact same lack of difficulty, and in less than a minute you'd removed both of Michelle's legs, rendering her a squirming, smiling, limbless pillow on your bed. Gathering up her limbs, one severed arm pinching your butt while a leg wrapped around yours and rubbed itself against you, you prepared for stage 2 of your first fantasy...