Lisa Comes Back With a Pump

The next several minutes, Diana sat in silence, her legs wide open. She felt the cold air against her folds, felt the harsh rope against her wrists. It was like the fantasies she had once had, kept to herself for fear of what they would mean and now finally unleashed to be played out in full. She imagined how many people were watching her right now, hundreds of them at least. All of them seeing her naked, all of them seeing her tied up and helpless.

Was this what she had always wanted? This feeling of helplessness? This arousal by domination? She had struggled with it for most of her life, trying to balance her desire for submission with her life as a top level student, but right now, all of that was falling away. She didn't care anymore. Everyone could see her, and she loved it. Lisa had been right, the rulebook was something truly special and truly amazing.

Speaking of Lisa, Diana heard her coming back again. She turned to regard her sister, seeing her carrying a strange looking device from one of the boxes along with a small bag of other assorted things. Diana had never seen that sort of device before. It consisted of a hand pump connected by a length of corded wire to a small glass receptacle, like a cup but smaller, and somewhat thicker as well. The glass ''cup'' was smaller than she would have expected were it to be for drinking, though also surprisingly deep for its size.

"You know what this is, Di?" Lisa asked as she approached.

"N-no." Diana admitted. "Though, it's not a hard thing to guess. It's a pump, right?"

"Right." Her sister nodded. "The chat wants to use it as part of your punishment."

So saying, Lisa came around the front of the bed. Diana remained where she was, sitting with her legs spread as her sister knelt down in front of her. So close up, she could almost feel Lisa's body heat on her naked skin.

Diana jumped as Lisa's hand gently stroked her mound, the shock of the unexpected contact sending lightning racing through her spine.

"L-Lisa!"

"Sorry!" Lisa said. "Sorry! I don't mean to be rough, but for this to work, I need a little action on your part."

"A little..urgh, a little action?" Diana repeated as Lisa's hand continued to softly toy with her pussy. Her fingers trailing along the line of her labia, teasing and probing as they rose higher. Diana felt her lower self twitch in response to the stimulation, her sisters fingers gently stroked the inside of her folds, tracing upwards slowly. Diana felt her pleasure building again, Lisa's touch left a tingling wake of desire as it moved, but it was clear that the younger twin was looking for something. Moving higher and higher until...

"Ah, there it is."

Diana felt Lisa's fingers gently close around her clitoris. The feeling like a lightning bolt from the blue. She tensed, pulling against the ropes that bound her arms behind her back.

"Don't get too excited." Lisa whispered to her. "This is supposed to be a punishment, remember?"

Before Diana could respond, Lisa gently placed the glass container over her clit. It felt cold against her hot skin. Lisa held it there for a moment, then reached for the hand pump.

"It's kinda funny that they should tell us to use one of these." Lisa said. "You know, I was going to use one someday? Always meant to, it seemed kind of fun, but I never got around to it." She laughed. "It's sort of embarrassing to admit that to my own sister, but after today, what does it matter? Do you know how they work?"

Diana shook her head.

"Oh, it's pretty simple." Lisa said, gesturing to the hand pump she now held. "It uses suction to create a vacuum, drawing blood to the clitoris. The feel of it sucking you is supposed to be pretty good too, but that's not the main reason people use it. You see, the clit has a lot of nerve endings, and blood circulation engages them all, making the clit as a whole a lot more sensitive. Also bigger, it becomes swollen and engorged with all the blood. Not terribly unhealthy, so long as you keep it to a minimum."

"You know all this stuff?" Diana shot her a look. "Why?"

"Well, like I said, I sort of wanted to try it out myself one day, so I did some research into it - don't wanna get into something you don't understand, right? I wanted to understand how it worked and why it does what it does. Now sit back and relax sis. Er, not that you have much choice."

Lisa pressed down the hand pump and the machine came to life. At first weakly, it began to cling to her lower self, the pressure growing stronger with each pump. Diana at first could only barely feel the weak pull, but as it grew more and more, she found herself gasping with each pump. The glass container clung tightly to her lower lips, centred on her clit. Each time that Lisa pumped, Diana felt herself grow a little bit bigger as more blood was pulled into her sensitive area, and her clitoris became engorged. It was a very strange feeling for something usually so small to grow like that, something she had not even known that she was capable of.

The suction pulled at her, making her clit strain with pleasure. It was like being gently teased with no pause or respite, the air pulling at her constantly.

After a few more pulls of the pump, Lisa set the handle down.

"Don't wanna go too far." She said. "That machine can be sort of dangerous if you overdo it. I think that's enough for now."