She takes the vibrator out

"Hmm. Well, I suppose I do need a first-hand report on what sex in bondage is like, and I'm not going to get that with you moaning and wriggling all over the place. So, OK."

You almost sob with relief and gratitude as she unfastens the crotchrope from your wrists, pulls it clear, then pushes a hand between your legs, grasps the base of the vibrator and tugs it out of you.

Without the crotchrope there's nothing holding the plug in your anus. You could try to push it out. What stops you is years of conditioning that the only proper place to push anything out of your ass is when sitting on a toilet. Doing it here, on your own bed, just seems gross.

Tentatively - "Aren't you going to untie me?"

"No way! Your little friend's not finished with you yet. Now - that was one hell of an orgasm you just had, wasn't it?"

Words stick in your throat. You don't like the sound of Debbie's threat.

"Don't go quiet on me Karen. I'll give you ten seconds, then this vibe's going back in, and this time it'll stay in."

God, no. Anything but that.

"Yes. Yes it was. I've never cum as strongly as that."

“Did you enjoy it?”

“No. It was scary. I was completely out of control. I couldn’t even breathe. I thought I was going to pass out.”

“Was it stronger than when you normally cum with the vibrator?”

“Yes – much. If it was usually like that then I wouldn’t use it.”

“So it must be the bondage. That’s worth knowing. I hope it’ll work with me and Karl.”

Typical of Debbie to leap straight to a conclusion that she wanted to hear from the start. It might have been the bondage. Equally, it might have been because your genitals were swollen and sore from the crotchrope. Or it might have been because you’d already cum three times before she put the vibe in. Or it might have been the butt plug. Or a psychological effect – the humiliation of having been tied up by your kid sister, or of having an orgasm in front of your best friend.

It doesn’t matter. She thinks that her experiment has been a success.

“So are we done now? Will you untie me. Please?”

“I think there’s something else we ought to find out. But I don’t want you rolling off the bed – let’s get you on the floor to start with.”

She busies herself taking cushions off chairs and padding the floor next to the bed. As she does so you wonder what’s going to happen to you that might cause you to roll off the bed. Hogtied as you are, you’re not exactly mobile.

Getting you onto the floor proves simple. She simply pulls the duvet, with you on it, off the bed. You drop eighteen inches to the cushions, which very effectively break your fall. Then a bit of rolling and pushing gets the cushions and duvet out from underneath you, leaving you lying on your own bedroom carpet.

“Uh – Debbie, why? Why do I have to be on the floor? Why might I have fallen off the bed?”

She doesn’t answer. Instead, she unties your knees.

You’re confused. Is she going to untie your other bonds? What does freeing your knees achieve?

Then it hits you. With your knees untied your legs can be spread a little, even with your ankles still bound. And with your legs spread…

“NO! Don’t.. Debbie, please don’t..”

She rolls you onto your back. It’s not a stable position – you’re balanced on the points of your elbows. But she only needs a second to part your thighs and push the vibrator, now turned on again, back into your vagina. She grips the rope over your belly as you roll back onto your front. A quick, hard pull and the rope is again buried between your labia before being tied off to your wrists.

“Debbie, stop it. Pleasepleasepleaseplease. Don’t make me cum.. Don’t make me cum like this..”

“Oh shut up. You said you didn’t know how soon you could cum a second time. Well, we’re going to find out. And we’ll also see just how many times you can cum.”

She reties your knees, then settles herself in a chair to watch you.

“No, please. Don’t leave me like this. I can’t stand it. Take it out. Please take it out. It’ll kill me. Oh God, I’m… Debbie please.. I can feel.. Ahh… Ahh… NO DON’T! Please Debbie, don’t. I won’t… mmmphhthhhh….”

Your last words are triggered by Debbie picking up the ballgag. You don’t want to be gagged. You don’t like being gagged. You’ll be completely helpless.

You ought to lock your jaws, but you’re moaning almost constantly under the effect of the vibrator, and Debbie easily pushes the ball into your mouth before doing the strap up tightly behind your head.

“hh ghd, hh ghd plmhfm dhn't lmt mm ghm. Hntnm mm. Thgm Hmt hht, plmhfm thgm Hmt hht."

"Hh Ghd, Hm'm ghmmnng! Hm'M GHMMNNGGGG....”

The next orgasm takes you.