( ・o・)ノ

The first time Kakashi had seen her new jutsu in action, he had been fascinated and scared out of his mind at the same time. An enemy had barely graced her white-green body aglow with sage chakra before they dissolved in a steaming puddle of blood at her feet. In seconds.

His student had become truly terrifying while he hadn't been looking. 

Years later, after the messy reunion of her old team, an elopement that resulted in the birth of her daughter, years of estrangement followed by a divorce, and a heartrending breakdown in front of his old teacher wondering aloud if she simply was unlovable, Sakura had found her way into Kakashi's bed. Over time, they had come to an agreement. It might not be love, but it was the next closest thing. 

Kakashi had been the one to suggest they tried this. That memory had been a constant at the back of his mind ever since Sakura made him discover he enjoyed a little pain with his pleasure. He always felt like he could melt into a puddle after sex. Why not try it out when there was a possibility of it actually happening?

Sakura had cautiously agreed to tweak the jutsu to cause minimal damage, with the condition of taking any time she needed to thoroughly research and test it before trying it out. A whole year had passed before she had told him it was finally completed. 

He was eager to find out the results.

Sakura was sliding effortlessly up and down on his dick later that afternoon, her body drenched in translucid white goo from head to toe as if she were soaked in cum. It made him burn in the best way. Everywhere she touched bliss and agony prickled at him and engulfed his thoughts.

"Does it feel good, to be such a pervert you're known in the whole village for it? Hm?" She increased the force behind her thrusts, making the juts of his hips ache when she slid down. Fuck, her strength was incredible. "Answer me. Are you enjoying having begged me to modify a lethal jutsu simply so you can get off on the pain of your slutty dick?"

He groaned, unsure if he could form words right at that moment, thrusting up into her several times in answer instead. Sakura smirked.

She touched his abdomen with a glowing green finger coated in chakra, and the sensations increased, making him cry out in surprise. It wasn't the first time Sakura had tweaked his body's sensivity to touch using her medical skills. She either could reward him with some of the most mind-blowing orgasms he had ever had, or torture him for hours with anticipation, turning him into a sweaty, frenzied, pleading mess.

Very soon, as his release neared, he opened his mouth to whine, to beg, to call the name of the only one who always made him feel this ecstasy. 

She grabbed his tongue, and pulled it out, and hissed in his ear,

"Pant for me like the randy dog you are, you degenerate, filthy sensei."

His muscles clenched and his vision blurred as his whole body became inundated with his orgasm. Kakashi thrust erratically into her old student two, three, four times, until he buried himself balls deep into her with a long moan and stilled.

Kakashi took big gulps of air, now feeling the fizzling of the acid slime in his mouth. Sakura waited until he had somewhat settled, then started chasing her own climax, taking her pleasure from his softening, oversensitive cock. He writhed despite himself, despite desiring to give her just as much as she had given him, but Sakura assisted him by pinning him to the bed with her superior strength.

Left with no other option, he laid back and watched how she picked up speed, brow furrowed, breasts bouncing, mutters of "Yes, yes, yes, yes yes yesyesyes-!" in a crescendo until she threw her head back with a triumphant cry. Then her hands glowed green on him, and he followed right after with barely a dribble of cum and a pained sob of pleasure.

After a few seconds, she cancelled the jutsus and kissed him passionately. Kakashi hugged her tightly to his chest and returned it, their tongues ravishing the other, speaking without words needed.

Kakashi was the first to break the kiss apart, breathless. They snuggled together, still connected, while they recovered. 

"This was…" Sakura shifted on top of his chest and he sucked his teeth at the feeling in his groin.

"Wonderful. Amazing. Fantastic. Promise we'll do it again?"
 
Sakura laughed tiredly, her walls squeezing him lightly along with her mirth.

"Another time, okay? Let me heal you and then we'll take a shower to wash all this goo away."

"Hmm." He smiled cheekily up at her. "Alright, but maybe later. My dick is still aching very nicely."

This time, when she laughed, she batted at his chest. She stayed until Kakashi had gone completely soft. Kakashi knew his injuries posed no danger with the best medical ninja of the whole continent caring for him; he just wanted to feel her like this a bit more.

He was incredibly grateful he had let her into his bed all that long ago.
 

I admit I barely knew about CBT before writing this. I've never found fic about CBT in the wild and some of the things I found researching online seemed very complex, so I decided to go the fantasy route where I make the rules about what's possible, safe, and pleasurable. It's a cop-out, but still, I hope the fic captured the essence of the prompt, or at the very least, that reading about whacky fantasy sex was entertaining. (And there might even be more realistic depictions of this kink coming up in future stories.) ;)