Sister sack-whacks

*(All characters in this story are over the age of 18. This story is in response to* [*a request*](https://www.reddit.com/r/BallbustingStories/comments/1awrxd4/playful_sibling_ballbusting_stories/) *by* u/JelloBoy1230.)

"Sack-whack!"

By the time Jacob heard those words, it was too late to react or protect himself. His little sister's hand had already smacked into the front of his sweatpants. His dick offered little protection, and the impact went right through to his balls. Pain shot through his crotch, and he made a strangled shout. He jackknifed over, and his hands shot downward, too late to do anything. Looking up, he saw his sister Emily laughing at him as she danced backwards, out of reach of any retaliation.

Jacob stood there, half bent over, trying with all his might not to let his 18-year-old sister see how much pain she had put him in. The two of them had always play-fought when they were kids, but had been careful not to actually hurt each other. Then a couple of weeks ago, just after he came home from college for the summer, Emily had seen him play-fighting with his friends. He had whacked his friend Mike in the nuts, and yelled "Sack-whack!"

That sack-whack had been a bad decision on Jacob's part. Ever since Emily had witnessed that, she had assumed that nut shots were a normal part of horsing around. So she had started hitting her older brother with surprise sack-whacks of her own. Jacob could have told her how much it hurt, but his pride wouldn't let him admit that his little sister could put him in agony with just a little slap. So he did his best to hide the pain, always fighting to stay on his feet and keep his expression as neutral as possible. As a result, Emily never fully realized what she was doing to him.

Now he looked over at his sister, laughing at him from the other side of the room. She was skinny and pale, with a cute round face and long straw-blonde hair. Jacob could have easily beaten her in a fight, yet here he was, fighting just to stay on his feet after one quick little slap from her tiny hand.

"I'm gonna get you for that," Jacob grunted at her, trying to smile and sound playful.

"Can't!", Emily teased. "I don't have a sack to whack!" And as if to emphasize the point, she slapped herself in the crotch. That slap would have devastated a boy, but Emily just smiled.

"I'll get you some other way," Jacob warned. "Just you watch."

"I'm ready for whatever you got," Emily said, sticking out her tongue. Then she skipped out of the room, still laughing.

As soon as she was gone, Jacob hobbled to a chair and collapsed into the seat, breathing heavily and waiting for the pain to go away. He thought about ways that he could retaliate against Emily for sack-whacking him. He had an idea.

A few hours later, Emily was standing at the kitchen counter, making herself a snack. As usual, she was wearing sweatpants and a t-shirt. Jacob quickly tiptoed up behind her, grabbed the waistband of her sweats, and yanked them down to her ankles. "Pantsed!", he yelled.

"Aaack!!", Emily yelled. To Jacob's surprise, he found that his sister wasn't wearing any underwear. He found himself face to face with her small, round, bare butt. Emily's hands shot down to cover herself, and she bent over, backing away from Jacob. Her face was blushing bright red.

"Oh my God, you pantsed me bare-ass!", Emily shouted. She was holding one hand pressed tightly over her crotch while she fumbled to pull her sweats up with the other hand. "Asshole!", she yelled.

Jacob had gotten over his initial surprise at her lack of underwear, and just laughed at her. "That's what you get for sack-whacking me," he said.

"I'm gonna get you," Emily warned as she finally managed to pull up her sweats and regain her modesty.

"Don't try it, or you'll get more of the same," Jacob said with a shrug.

But Emily wasn't deterred. Just two days later, Jacob was bent over on his hands and knees, untangling the cord of his Playstation 5. Suddenly he felt an impact smack into his balls from behind, through his jeans. At the same time, he heard his sister's voice shout "Sack-whack!!"

This slap was even more painful than the last. It connected directly with the vulnerable underside of his balls. And since they were trapped in his tight jeans, they had nowhere to go. Pain immediately washed over Jacob, and before he could stop himself, he made a high-pitched squeak.

Jacob immediately pitched over onto his side, holding his nuts. He heard his sister laughing at him. Making a mighty effort, he rolled over and fought to his knees, overcoming the pain through sheer act of will. Emily had collapsed backward onto the couch, cackling with laughter.

"I told you I'd get revenge!", she giggled.

Jacob was in too much pain to respond instantly. He focused on getting to his feet. Nausea was shooting through his stomach, but he managed to struggle upright. There he stood with his hands on his knees, red-faced and breathing heavily.

"OK, he wheezed. "It's war."

"What are you gonna do, pants me?" Emily taunted him. "Like I care about that!" To demonstrate this, she hopped up off the couch, turned around, and pulled down her sweatpants, mooning her brother. Then she pulled her sweats back up, turned back to him, and stuck out her tongue.

"You'll see," Jacob warned. Emily walked over and patted him on the head, then skipped away with a huge grin on her face.

As usual, Jacob waited until she was gone to collapse and recover. His faced was flushed and burning with shame, and his mind was racing as to how he could get his little sister back when she didn't have any balls to attack. Finally he hit on a plan.

Emily liked to read in the living room in the evening, and she used the overhead light that hung down from the ceiling. A few days after his latest sack-whack, Jacob carefully replaced the bulb with a burned-out one. When his sister went to read that day, and discovered that the bulb was out, she decided to replace it. That required raising her arms above her head as she unscrewed the old bulb.

As her arms were raised above her head, Jacob snuck up behind her. He grabbed the bottom of his sister's t-shirt and yanked it all the way up over her head, imprisoning her arms in the up position. Emily shrieked and thrashed around, unable to escape her shirt. As expected, she wasn't wearing a bra. Jacob was amused by the sight of his sister's small breasts as she struggled ineffectually.

This was part of Jacob's plan. He stepped behind the thrashing Emily, reached around, and grabbed Emily's exposed nipples with his thumbs and forefingers. "Tiddy-twister!!", he shouted as he clamped down and pinched.

Emily shrieked again, struggling and thrashing around as her brother assaulted her nipples. She kicked back at his legs, and pitched forward onto the floor. Jacob went down with her, giving her nipples one last pinch and then letting her go and standing back up.

After a couple seconds, his sister managed to get her shirt back down. She looked up at Jacob, red-faced. He just grinned down at her. "That's the punishment for sack-whacking me," he said.

"You total asshole," she said, but as she said it she grinned too. "You got me good. It's on."

Jacob walked away, putting on a brave smile, but worried that he hadn't managed to deter Emily from further sack-whacks.

For the next week, he carefully kept an eye on her, making sure never to leave himself open to attack. She just grinned at him and occasionally flicked her hand in the direction of his crotch, watching him flinch and laughing at his reaction. The fake sack-whacks were almost as humiliating as the real thing, because they reminded him of how vulnerable he was to his little sister.

But Emily's patience paid off. After a week, Jacob let down his guard, and fell asleep in a chair in the afternoon. He was woken up by a blast of pain, as his little sister's palm slapped directly into the crotch of his shorts. "Fuck!!" Jacob shouted as he woke up and immediately felt agony wash over him.

Emily was standing over him, laughing her ass off. Jacob clapped both hands over his agonized nuts and rolled onto his side in the chair. He turned his face away from his sister, not wanting to let her see how much pain he was in.

But Emily wasn't done. She ran over to him and reached her arms around his sides. She grabbed her brother's nipples and shouted "Tiddy twister!!", pinching with all her might.

The tiddy twister hurt, but Jacob didn't dare take his hands away from his crotch. He knew that if he did, Emily was likely to give another whack to his already tenderized sack. So he thrashed around, trying ineffectually to dislodge Emily's hands from his nipples and shouting "Let go!". Eventually Emily let him go, giving him a slap on the butt and dancing away.

"See?", Emily taunted. "Two can play at the tiddy twister game."

"I'm gonna get you so bad," he moaned.

"Yeah, how?" she asked teasingly. "Sack-whack beats everything."

Jacob wondered if she might be right. But he resolved to try one more thing. This was war, and he was going for the nuclear option.

Two days later, Emily had just gotten into the shower. Jacob knew his sister didn't lock the door. He put on his swim trunks and took off his shirt so he wouldn't get wet. Then he barged into Emily's bathroom, banging open the door. "Hi, Em!" he shouted cheerfully.

"Oh my God get out!", Emily shouted. But instead, Jacob yanked back the shower curtain, revealing his little sister in her full nude glory under the running water. Emily screeched and covered her breasts with one hand and her crotch with the other.

But Jacob didn't hesitate. He reached down and grabbed his sister's legs at the knees, putting his shoulder into her midsection. As she thrashed and screeched, he lifted her up and out of the shower. Leaving the water running, he carried his soaked and naked sister into the living room. There he threw her down on the couch.

Before she could defend herself, Jacob reached down and began to tickle Emily mercilessly. She shrieked and rolled onto the floor, trying to protect her armpits with her hands. Jacob bent over and tickled her ribs. She screamed and writhed, but there was no escape. In the meantime, of course, Emily was completely incapable of covering her nudity, leading to further embarrassment.

Then in an instant, just as Jacob was getting his ultimate revenge, the tides turned. As Emily thrashed and kicked her legs, one of her wildly swinging feet landed right in Jacob's crotch. His swim trunks offered no protection whatsoever, and he immediately doubled over.

Jacob emitted a high-pitched wail of distress, as pain much worse than any sack-whack overwhelmed him. He didn't think about hiding it this time. In fact, he couldn't really think of anything except the agony in his balls. He fell to his knees, then onto his side in a fetal curl, rolling on the carpet and moaning.

Emily, suddenly triumphant, leaped up off the ground. She immediately bent over her fallen brother and pulled off his swim trunks, easily overcoming his feeble resistance. Now he was as naked as she was, and she no longer felt embarrassed at all.

But as Jacob continued to thrash and moan on the ground, Emily suddenly felt a stab of guilt. She had always thought that sack-whacking her brother only caused him a little pain and a few moments of paralysis. Now, watching him in agony at her feet, she realized how much a nut shot could hurt a man. Emily had never wanted to really hurt her brother. She had just wanted to tease him. Now she realized things had gone too far.

Emily bent down and rubbed her brother gently on his back, asking "Are you OK?" Jacob was unable to answer for several minutes. Emily tried to comfort him as best she could. Then eventually he rolled onto his back, and Emily saw that her brother's face was wet with tears.

"I'm so sorry, Jake," she said, rubbing his hair gently. "I didn't mean to hurt you."

"It's alright," Jake gasped. After another couple of minutes he had recovered enough to look his sister in the face.

"Emily," he said hoarsely, "my balls are really vulnerable. I don't think you realize that."

"I'm sorry," she said again. "I didn't know."

"It's OK, it's my fault," Jacob said. "I should have told you. Instead I always tried to be a tough guy and hide the pain when you sack-whacked me."

"Oh my gosh," Emily said, putting her hand over her mouth. "How bad was I hurting you?"

"Just don't whack my sack for fun anymore, OK?", Jacob laughed weakly.

"I promise I won't," Emily said. "Your sack is now off-limits to whacks."

Jacob laughed. "You won, little sis," he said. "You were stronger than your big bro."

"Wow," Emily said, looking down at her brother's exposed balls. "Girls really are the stronger gender."

They laughed. "Do you forgive me for hurting your nuts?", Emily asked.

"Of course I do," Jacob said. "You're my little sis."

Emily leaned down and gave her brother a hug. He hugged her back weakly, wincing from the pain still shooting through his abdomen and crotch.

"Hey," Jacob said to Emily. "You're butt-ass naked. Why don't you go put on some clothes?"

"It's OK," Emily said. "I'm not embarrassed. I don't have something vulnerable to protect." And to emphasize this, she slapped her bare crotch with her hand.

"GET DRESSED," Jacob said. "That's gross." Emily laughed and bounced away to put some clothes on. Jacob wanted to follow her, but the pain was still too much, and he couldn't get up. Instead he just lay there waiting for it to subside.

He had been thoroughly and completely defeated and humiliated by his little sister. But somehow he didn't mind as much as he thought he would. In fact, the whole thing had been kind of fun.

*(The end)*

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