"Uuu..."
Her pink eyes were brimming with tears, and her petite shoulders shook with rage.
That "file" of a chest, with its prominent ribcage, had rubbed against Rin until it was red, but she couldn't produce any results. Watching Juju looking like she was about to cry, Rin Ito pursed his lips to stifle a laugh.
"Maybe stop 'filing' me? Or should I just give it to you?"
Juju's lip twitched, revealing a small snaggletooth as she shot a murderous glare at Rin.
"I'll file you to death!"
"Cough, cough... okay, keep going, keep going."
Snaggletooths are dangerous to a man's pride; Rin didn't want to test that sensation, so he could only let her continue her "filing."
If he used his hands, her small chest was cute, but being rubbed by it wasn't exactly comfortable. It was so barren and thin that any pressure resulted in the feel of bone against skin.
As expected, someone like Shinju was much more comfortable. Of course, Rin couldn't say that to Juju. This "filing" was starting to get painful.
Flat chest aside, Juju was completely inexperienced! Even with petite girls like Fairy or Sagiri, it was fine, but Juju... well, even without actually "eating" her, there were other ways to play.
Juju was currently using her hands to desperately try and squeeze what little flesh she had into a cleavage. Seeing this...
Before Juju could explode in shame, Rin grabbed her under her armpits and lifted her up. Before she could react, he turned her around and sat her down in his lap.
"GUH!!!!"
The moment Juju sat in Rin's lap, her eyes nearly rolled back... remember, she still had a "little tail" in her ass.
As she sat, the entire plug was buried deep inside her rear. The spot that had just been tortured by her ribcage was now perfectly aligned with the triangle between her legs and her wet lower abdomen.
"Everyone has strengths and weaknesses. You have to play to your strengths... This area right here is your strongest point. Have you ever heard of '素股' (Sugu - intercrural sex)?"
"Wait..."
Before Juju could finish, Rin lifted her slightly. The plug that had almost vanished into her ass was pulled out a bit, and then...
With a momentary sense of weightlessness, Juju dropped back into Rin's lap. The dual stimulation, a sensation she had never experienced, caused wanton moans to replace her tsundere insults. This feeling of being completely enveloped and the intense friction was far more comfortable than using her chest as a file.
It wasn't just good for him; it was good for Juju too. Stimulated on both sides and already made hyper-sensitive by Kaede's earlier "training," Juju's body tensed up and reached its limit after only a few rounds.
But Rin wasn't going to let her off that easily... He believed in fairness. Since he gave the younger sister a load, he had to give the older sister one too.
After being "filed" for so long, Rin didn't relax until Juju had reached her fourth climax.
For the sister, Shinju, it was from top to bottom. For the sister, Juju, it was from bottom to top. The only thing they shared was the feeling of heat splashing against their cheeks.
Juju sprawled in Rin's arms for a long time. Once she regained some strength, she scrambled out of his lap and ran to the bathroom to wash her face.
As she ran, the little tail behind her swayed back and forth, looking exceptionally cute.
A short while later, a much more sober but highly embarrassed Juju returned to the living room. Her pink eyes were no longer tearful, replaced entirely by indignant shame.
She walked up to Rin and said nothing, just glaring at him with pure venom.
"Ahem..." Rin cleared his throat, ignoring the fuming Juju. "It seems you've adapted to the 'little tail.' Now, let's talk about the training plan. Take the tail out first."
"Hmph..." Juju snorted but didn't protest. She turned slightly and pulled the plug out of her ass. Before handing it over, she inspected it carefully to make sure it was clean.
Rin wasn't worried about messes. Normally, Kaede would redeem a "Temporary Body Cleansing" buff. In fact, Kaede hadn't just redeemed it for Juju today; she'd done it for Suzune, Sayu, and Saki as well.
While Rin was training the Kanai sisters, Kaede was helping him "train" the others.
Under Juju's confused gaze, Rin pulled out a piece of gear that looked like leather panties. It featured strange slots and... a lock?
Under Juju's suspicious eyes, Rin attached the tail plug to the gear.
"Now, let me introduce you to the true usage of these items."
"Wait a second!!!" Juju swallowed hard. "You... you aren't suggesting I wear those panties, are you?"
"Bingo~" Rin nodded with a smile. "This is originally called a chastity belt. As the name implies, it protects your chastity. Once locked, no one else can touch you. However... we can add attachments for 'training' purposes."
Gulp...
Juju swallowed again.
"Looking at the slots, you can see it can plug both the front and the back. Since you're a virgin, Juju, we'll swap the front one for something else... Put it on. I'll explain the specific functions once it's on."
"..."
"Put it on," Rin said with a wink and a smile. "It's for Shinju's sake~"
"...Fine. This is for Shinju."
After a moment of hesitation, Juju bit her lip and guided the plug attached to the belt into her ass. With a crisp click, Rin locked the chastity belt into place.
"Mmm..."
Juju wiggled her body and took a few steps. Aside from a sense of fullness in her rear, it wasn't uncomfortable. Then she tried to pull at it, but no matter how she struggled, she couldn't get it off.
"Where's the keyhole? Why isn't there a keyhole?"
"This is a high-end IoT product. It's permanently connected to the network. Unless I unlock it with my phone, you can't take it off."
In reality, these were all toys Kaede had redeemed. Nominally, Kaede "bought" them, and Rin just played along with the lie. It was all the same in the end.
"It's not just the leather panties. That little tail is also a smart device. It's packed with sensors that monitor data like internal pressure. And..."
Rin smirked as he pulled out a small electrode pad, similar to a physical therapy device. A wire ran from the plug to the electrode, which he then stuck onto Juju's stomach, right over her "baby room" (womb).
Juju recalled some videos she'd seen... not erotic ones, but challenge videos where influencers put electrodes on their hands and tried to drink soup while being shocked.
"Is... is this... is it going to shock me?"
"Smart girl~" Rin's lips curled into a delighted arc. "This electrode will discharge if you break the rules. But as long as you follow the training rules and behave, you won't get shocked~"
"Rules...? What rules?"