"R-rules?"
Juju looked down at her "equipment" and her lip twitched.
"Don't be so tense. These rules are for your own good." Rin pressed his lips together to hide a grin. "After all, you wouldn't want to break your body, right?"
"..."
Though she was chasing that pleasure from before... no, though she was doing this to help Shinju, she didn't want to wreck her health.
Seeing Juju turn serious, Rin cleared his throat. The "breaking the body" part was actually a lie. With the System Daughter watching, he wasn't worried about Juju's safety at all.
Even if the play became much more extreme, she'd be fine.
"It's not just the electrode that can shock you; the tail in your ass can discharge too... Don't worry, under normal circumstances, neither will fire."
Hearing that, Juju finally let out a breath. Though she hadn't been shocked before, she knew being electrocuted in such delicate places would be agonizing.
"As I said, these have sensors. If they detect that either the electrode or the tail has left your body, the other side will discharge continuously until the connection is restored."
"What about using the bathroom or showering?" Juju knit her brows.
"Relax... I can unlock the belt and everything else remotely. I'll unlock it for you every day for your hygiene routine. These settings are just to prevent you from taking them off privately. As long as you don't mess with them, you won't be shocked."
"That's more like it..." Juju muttered.
"Don't get happy too early. Just not taking it off doesn't mean you won't be shocked... The main function of this set is to supervise your exercise." Rin paused, looking completely satisfied. "The rear is delicate. If it's expanded for too long, it won't snap back... You don't want to spend the rest of your life in adult diapers, do you? So, expansion must be paired with muscle training."
"From now on, the vibrating egg and the tail in your ass will vibrate at random intervals. Juju, your job is to squeeze your muscles as hard as you can. Once the sensor in the plug detects enough pressure, the vibration will stop."
As Juju listened, she felt something was very wrong...
"It stops when it feels enough pressure..." Juju had a terrible premonition. "And what if it doesn't feel enough pressure?"
Rin gave her a wink and a smile.
"If it doesn't feel enough pressure, it will start shocking you to 'help' your muscles contract." Before Juju could protest, Rin pulled out his phone. "Now, for a test."
"Wait— Mmph!!!"
The moment Rin spoke, Juju felt a vibration. If she weren't locked in, she felt like it would have slid right out of her.
"10... 9... 8..."
"A countdown? What are you counting down for?"
"Asking a question counts toward the time, too. 3... 2... 1."
"EEEYAAAHH!!!"
A numbing electric shock instantly surged from the electrode on her belly and the plug in her ass. A split second later, the tail and the pad sent a current directly through Juju's most sensitive spot—her womb.
"OH-HO-HO-HO-HO-HO-HO!!!!"
Juju's eyes rolled back as her abdominal muscles and sphincter tensed instinctively. Between her trembling legs, a clear stream of fluid slid down her thighs. She curled into a ball on the sofa, clutching her stomach, and it took a long time for her to sit back up.
"Hah... hah... that was... so... f-f... that was way too perverted!"
Realizing she almost said "good," Juju quickly corrected herself. To be honest, it had been a long time since she felt that good. Juju had finally revisited that sensation of being stimulated at her absolute deepest core.
It wasn't quite the level of the parking lot or the manor party, but it was satisfying enough.
"That was just a penalty. As long as you squeeze hard during the vibration, you won't be shocked. Although... you seemed to enjoy it. If you weren't wearing the belt, you probably would have squirted."
"I... I did NOT! How could I enjoy that! It was the electricity!"
Rin smiled and didn't call her out. Instead, he started another test with a wicked grin.
BZZZZZT...
"!!!!!" Juju's gaze sharpened. She immediately used every ounce of strength to clench her ass while counting down in her head. When she hit zero, the vibration died. Juju let out a long breath.
It felt good, but she couldn't do this continuously.
"That's the feeling. It's to train your rear. The vibrations are random. During the day, it's about twice an hour. At night, about once every two hours. Ten seconds in the day, twenty at night... Any other questions?"
"Wait, what if it starts vibrating while I'm in class!?"
Juju visualized herself being called on by a teacher to answer a question, only for the tail in her ass to start buzzing. If she didn't clench hard enough and got shocked... Even though she went to an all-girls school, it would be social suicide if anyone found out.
Going to school in locked panties with toys inside... Juju shook her head frantically to clear the nightmare from her mind.
"Don't worry. These are silent products. As long as you don't let any weird noises escape your mouth, no one will notice."
"R-really?" Juju frowned deeply.
"Of course. Someone at the Baumkuchen celebration was wearing a similar toy. Did you notice?"
"...?"
Juju tilted her head, completely stunned. She had guessed the Baumkuchen girls were involved with Rin, but this... this was just too depraved!
As expected of a circle run by an adult manga artist!
After letting Juju shower again in the hotel, Rin finally took her home.
In front of her house, Juju guiltily checked herself over. Her uniform was clean and crisp. No abnormalities... at least on the surface.
Her gait was a bit awkward at first, given the plug was stretching her open, but she adjusted after a few steps.
The electrodes and the lock weren't visible under her clothes. Her parents and Shinju shouldn't find out... With that thought, Juju took a deep breath and unlocked the front door.
"I... I'm home."
"Welcome back, Sister."
Shinju greeted her with a warm, healing smile that almost felt maternal. Looking at that smile, Juju felt a weight lift from her heart.
It's worth it. For Shinju's smile, the training and everything else is worth it... The pleasure is just a side benefit.
"Have you decided on your next cosplay, Sister?"
"The cosplay is... !!!!"
BZZZZZT...
Halfway through her sentence, the tail in her ass began to vibrate. Juju stood up perfectly straight in an instant. No, not in front of my sister!!!
OOOOOHHHHHH!!!!!!
She clenched her ass with every bit of power she had. When the vibration finally stopped, Juju let out a long sigh.
"I-I'm a bit tired, I'm going to my room!"
Shinju watched her sister's retreating back with curiosity. Sister looks... happy? And did she put on makeup? She looks even cuter than usual!