In his 18 years on earth, Sam Jackson had always gotten along pretty well with his twin sister Jill. They had a simple rule between them that had always helped to keep the peace — "Paybacks are Hell". The idea was if one of them did something wrong to the other, the payback would always surpass the original damage. So if Sam accidentally broke Jill's sunglasses, the "Paybacks are Hell" axiom would mean he would have to buy her two new pair. While this simple arrangement had always worked to avoid conflict, it also ended up leading to a very unexpected event.
It was springtime, and their parents were out of town for a few weeks, leaving the two of them on their own. They were both finishing up their senior year of high school, so you might think it would be a pretty good time to have your parents leave for a few weeks. Most high school seniors would have a two week beer and sex bash if their parents were out of town, but Sam and Jill were not that typical. In truth, they were both kind of nerdy. They looked and dressed pretty plain, didn't have a lot of friends, and neither had done much dating. So most of what they were doing with their parents out of town was pretty much what they did when their parents were in town.
One exception was that with their parent's gone, they were both taking advantage of using their master bath, which was much nicer than the bathroom they shared. It was a big fancy marble bathroom with a spacious tiled shower and a jacuzzi tub. The bath was only accessible from the master bedroom, and didn't have a door. Sam and Jill would take turns using the fancy bath, it was generally easy to tell if someone else was in there.
But as fate would have it, on an early Friday afternoon Sam decided to take a shower at the same time that Jill was getting out of the tub, and when he waltzed into the bathroom, there was his sister, standing stark naked in front of the tub. Even though it was his sister, his first response was to thoroughly check her out, which he was able to do because she didn't see him walk in initially. What he saw surprised him. His sister, generally covered in non flattering clothes, looked pretty smoking hot without any. She had shapely breasts and a toned body, with great curves and perfect legs. He was taking all this in instead of backing out of the bathroom, which would have been wiser.
"What the hell are you doing?" screamed Jill, grabbing for a towel and covering up.
Sam was back to reality in a hurry, stammering some kind of excuse as he turned and walked out of the bathroom. He kept walking back toward his room as Jill continued to yell something about privacy, but his mind was still frozen on the gorgeous image in front of the tub. He felt bad that he had barged in on her like that, but he was stunned and intrigued at how hot his sister looked naked.
It was a few hours later before he would see her again to apologize. He was in the kitchen making some cereal for dinner when Jill walked in, wearing a robe and glaring at him.
He couldn't help but grin. "Hey I'm sorry sis, I didn't know you were in there," he said. "It was an honest mistake."
She was still mad. "I didn't even hear you creep in," she said. "How long were you there?"
"I wasn't creeping, I was just coming to take a shower," he replied. "And I really didn't see anything, I mean, it was just a quick glance."
"Really, you didn't see anything?" she said hopefully.
"Just a quick glance," he said. Then after a moment, "But damn you got a hot body."
She threw an apple at him that just missed his head, but she also blushed and gave a half grin. "You're a total creeper," she said. "Sneaking up on your naked sister like that."
Sam laughed again. "Hey I said I was sorry."
"Not good enough," said Jill. "You know the rule, paybacks are hell."
Sam groaned. Jill was pretty good at coming up with brutal paybacks. He was expecting to have to clean up her room, or do her laundry, or do the dishes. But his expectations were wrong.
"You saw me naked, so I get to see you naked," she said flatly.
Now it was Sam's turn to blush. And also to choke on his cereal. "What?"
"It's only fair, you saw me and paybacks are hell, so now I get to see you," she said, even more resolutely than before.
While the initial thought in Sam's mind was that there was no way he was going to get naked in front of his sister, another train of thought started to filter in, and thinking about the idea of being naked in front of a girl, even if it was his own sister, was starting to sound kind of...hot. He didn't have a lot of luck or experience with girls, at least this was something.
"So you actually want me to let you see me naked?" he said.
Now Jill had actually expected Sam to strongly reject the idea immediately, so suddenly she was having some second thoughts about the request. But she had opened the door and didn't want to be the one to back down.
"Seems only fair," she said.
Sam's initial shock and reluctance had now been fully replaced by the notion that being naked in front of a girl, even a girl who was your sister, had a certain excitement to it. "Ok," he said.
Jill blinked. "Ok what?"
"Yes, ok I will let you see me naked as payback," Sam said.
"Oh, well, ok then," said Jill, trying to not act shocked. In the back of her mind she was wondering if Sam was really serious or pulling her leg.
"So where do you want your payback?" Sam asked.
Jill hesitated, wondering if this was really happening. "Well, uh, I suppose we should return to the scene of the original, uh, crime," she managed to stammer out.
Sam was surprised that she was continuing to go along, but he wasn't about to stop. "Let's do it now," he said.
By the time they reached the master bath they were both starting to have second thoughts, but neither was willing to show it. A blushing Jill took a seat opposite the bath, where she had previously been standing naked, to watch her brother.
Sam was wearing a t shirt and jeans, and he figured that after he took off his shirt Jill would probably call the whole thing off. He pulled the shirt off over his head and tried to flex his muscles. He was fit, but not muscular by any means, so his efforts caused Jill to giggle. She wasn't calling his bluff, so he unbuttoned and unzipped his jeans, stopping to look at her to see if she was stopping. She had one hand over her mouth covering a blushing smile, but nothing on her face said stop, so he dropped his pants off so he was standing there in only a pair of gray boxers.
Suddenly things were getting real, and Sam had to calm himself, his heart was thumping in his chest from a combination of nerves and arousal. Watching his sister looking at him nearly naked was having an effect. Meanwhile, Jill was fighting off a combination of nerves and the realization that her brother looked a lot better half naked than she ever thought he would.
"So, you sure you want me to do this," Sam said nervously.
"Yes. I mean, well only if you want to," Jill answered.
Sam took a deep breath and put his thumbs into the waistband of his boxers and then slowly, carefully, pulled them down over his cock and exposed himself to his sister.
"Wow," she said, before she realized she had even said it. Her brother had a nice looking cock dangling between his legs.
Sam's first response to being naked in front of his sister was to be nervous. His chest was pounding, he was shaking a little and he was having trouble breathing steady. He couldn't look at his sister, opting instead to look off in the distance. Gradually he began to relax some, and he started to kind of enjoy the feeling of being naked and exposed. Then he happened to look at Jill's face. She was staring at him, specifically staring at his cock, and her mouth was hanging slightly opened and she was mesmerized.
Her attention, especially her attention to his cock, was making him aroused, and though he tried to fight it, his cock slowly and gradually began to grow, and then edge upward. He was desperately trying to stave off an erection, but he was losing. Once his cock reached the halfway point, semi hard and pointing straight out, the battle was lost. It just kept on getting harder until he was rock hard and pointing towards the ceiling. Jill was mesmerized watching his cock grow, and impressed with the final result. There was no way she could deny or hide it, she was gawking at her naked brother, and in a moment of shock, realized that she had become quite aroused. By the time she looked back up at his face he was wearing a big grin.
Caught staring, she got flustered and embarrassed. "Ok, well I guess that payback is paid off," she mumbled. "Very nice." Then she got up and walked out and went to her room, leaving him standing there with a massive erection. He was embarrassed over her abrupt departure, and assumed it was because of his aroused state. Eventually he collected his clothes and made his was to his room. He wasn't able to make his erection subside at all, and ended up jacking off thinking about his sister watching.
They didn't see each other until late the next morning, getting coffee in the kitchen. She mumbled a good morning.
"Hey sis, I'm sorry about last night, I kind of got carried away I guess," he said.
"What do you mean?" she asked.
"Well you know, the whole getting a boner thing," he said.
"Ah, I do have to admit I noticed that," she grinned. "No worries, paybacks are supposed to be hell."