All characters are over the age of eighteen

*****

I watched her tight teenage ass sway back and forth as she walked through the hall in front of me, her black yoga pants hugging her long legs and ass perfectly. We made our way out to the parking lot and toward her truck. I knew that she was up to something but I hadn't yet figured out what it was. As we got close, I ducked behind a car three or four spaces over, careful not to be seen. And then I waited.

It was the third time that week that I had followed Kara out to the parking lot like this. If she had known I was there, she would probably have freaked out, but I had to figure out what she was up to.

Isn't that what brothers do?

Now, it was no secret that my eighteen-year-old sister was a slut. She was hooking up with new guys all the time. I knew of quite a few guys at our high school that she had been with. She had even been going out with guys from the local college. Not that it really mattered to me, wasn't my problem.

A couple of weeks before, I had walked out to my car at lunch to get something. I was parked only a few spaces away from her black Tahoe SUV and saw her climbing out of the back seat, followed by one of her guy friends. I wasn't one hundred percent sure but I could have sworn that he tucked a small fold of cash into her waistband as she finished buttoning up her blouse.

They had obviously just finished messing around but seriously? Had he paid her?

I needed to know for sure. It wasn't that I was protective of her or anything. She had made it perfectly clear that she would do whatever she wanted. It was more to satisfy my curiosity and maybe something to have for leverage in the future. She certainly had held things over my head in the past as blackmail so it would be nice to be able to get her back.

That's when I began following her out to her truck during our lunch break. She didn't come out to the lot every day, but it was pretty regular. So far I had seen her sneak into her truck with three different guys. Two of them were from her group of friends and the other was some football player. But I hadn't seen any type of "money exchange" like I thought I had seen before. I was beginning to think that she had simply found a new place to hook up.

A few minutes after arriving at her truck, I saw one of the same guy friends as before show up and climb into the back seat with her. Twenty minutes later, he climbed out and left, followed by her a couple of minutes after. 'Hmmm...' I thought to myself. 'I need a new plan.'

For the next couple of days, I racked my brain with a plan to see inside her truck. I needed to see and hear inside there if I was going to find out what was going on. Then it hit me. I had bought a wireless webcam months ago for a science project. I'd needed to be able to see inside a container and observe my test subject, which was just a small plant, without opening it and exposing it to any type of light. The project had earned me a C- but the camera had worked great.

That weekend I woke up early and snuck out to Kara's truck. The camera was small and slim so I was able to hide it in the pocket behind the passenger seat. I hid it in between a scrunchy and notebook that were already in there. Unless she pulled the items out, there was no way she would see it. Now I would just have to wait until another one of her hookups to see what that little tramp was up to.

It wasn't until Thursday that I saw her head out towards her truck during lunch again. I had tested the camera on Monday. As long as I was within a few parking spaces then I would be able to pick up the camera's signal on my tablet. I had parked close to her truck all week waiting for an opportunity.

Kara walked across the lot to her Tahoe. She had started parking further back in the lot, probably for more privacy. At one point, I thought I was busted when she turned and looked right in my direction. Her sunny blonde hair was tied up in a curly ponytail and I swear that her bright blue eyes had met with mine before she climbed into the back seat of her truck. I must have ducked down just in time because she continued into her truck and closed the door.

I made it to my truck and climbed in. My truck was a bit older than her SUV but it was a good truck. It had close to 100k miles on it but it had a big crew cab and hadn't failed me yet. I knew she wouldn't be able to see me through the dark tint of my windows and I turned on my tablet and remotely turned on the camera.

When it finally loaded up, I could see Kara waiting in the back of her truck. She was texting as she waited for whoever was going to show up today. As I watched, I started looking her over. It was no wonder why she got so much attention. Kara was gorgeous. Her blonde hair went down to her shoulders and she had a beautiful face with a pretty smile and dainty nose. She was athletic and fit from years of sports.

Today Kara had apparently dressed for the occasion. She was wearing a pair of cutoff shorts, the ends of the pockets sticking out just an inch or so past the frayed hem in front. Her long, smooth legs led down to her cute feet, her flip-flops kicked off onto the floor. She wore a thin black t-shirt that hugged her nicely and was cut down just enough to show off a sexy bit of cleavage.

A moment later, the door opened and a guy climbed in beside her. It was the football player that I had seen once before. He looked excited and eager like he had been waiting all day for this. Which he probably had.

"Hey!" he said.

"Hey, sweetie!" Kara greeted and set her phone down. "You ready to have some fun?"

"Uh-huh..." he replied, almost nervous.

Kara leaned in and kissed him. She half crawled onto his lap and turned him to putty almost instantly. As they made out, his big meaty hand reached down and squeezed her ass. After just a minute or two of this, Kara scooted away from him, lying back against the opposite door. She unbuttoned her shorts and slowly slid her hand into them, the slight rubbing motion indicating that she was rubbing her pussy.

"Common... take it out, baby, play with me..." she directed in a sultry voice. He did as he was told and unfastened his jeans. Pushing them down slightly to release his cock into the open. It was probably average length but pretty thick. He took hold of it himself and began to stroke it.

His eyes were fixated on Kara's hand as she also masturbated. They continued like this for a few minutes, Kara teasing him as they did.

"Play with that thick cock..." she would say. "Jerk it for me, baby, faster..."

The poor guy just sat there playing with his own dick and doing as he was told. His eyes lit up when Kara pulled her hand out and started sliding her shorts off.

"You want to see my pussy, baby?" she asked as she slowly pulled her shorts down until just the top of her shaved mound was peeking out. "I didn't wear any panties today, Matty, just for you..."

That's what his name was... Matt. I remembered having a class with him in the past.

He nodded his head quickly up and down. Watching intently as she removed her shorts. True to her word, Kara didn't have any panties on. My eyes were just as stuck on her pussy as his were as I saw it for the first time. Sister or not, Kara had the sexiest pussy I'd ever seen. Shaved bare, her tiny clit barely peeked out through her thin labia. Her slit was moist from arousal just barely peeking apart. 'Thank you high def cameras!' I thought to myself.

I had been so caught up in the show that I hadn't realized I was rock hard myself. 'Holy fuck, you're getting hard over your sister!' I scolded myself. But I couldn't look away. As she started fingering herself and rubbing her fingers in little circles around her clit, I rationalized that it was ok. That I would get hard watching any hot female doing the same thing.

I continued to watch my sister play with herself. I didn't dare touch my own dick though. That would take it too far. She pulled her top up over her bra with her free hand. Unclasping the front snap of her bra and freeing her tits. Another first for me. I had seen her in bikinis of course but it still wasn't the same as seeing Kara's perky teenage breasts on full display. They were the perfect size for her thin frame: large hand fulls of creamy white skin topped with pale pink nipples. They were amazing.

For the first time since arriving, the guy made a full sentence.

"I want you to do it for me this time," he said.

"You want me to jerk you off, hun? You want me to stroke that cock and make you cum?" Kara smiled.

He nodded 'Yes'.

"You know the deal. You okay with that?"

Again he nodded.

"Okay... sit back for me," she ordered. He turned and leaned back against the door. Kara sat up and scooted close to him. Laying against his side she rested her head on his chest and took hold of his cock. She began to slowly stroke it up and down in her hand. Pulling it close to her, she rubbed the tip of his cock against her nipple, smearing his precum around her pale areola.

"Emmm..." he groaned lightly when she began speeding up her stroking.

Kara rubbed Matt's thick cock against her tit as she masturbated him. Stopping for a few seconds, she held it upright as she spit a small amount of saliva down onto it to lubricate her handjob. Then, with increasing speed and a firm grip, she began jerking him again. Within moments she had him grunting and near climax.

"Ugh... ugh... ugh..." his hips slowly began to thrust upwards. Kara reached down with her other hand and continued to rub herself.

Finally, his thrusting became more powerful.

"That's it, Matty... cum for me... cum on my titties..." she urged.

And he did.

An eruption of white semen jetted out from his cock and across her breast. One after another, thick white ropes covered my sister's breast and nipple, some of it even reaching her side, near her ribs. She continued to jerk him, coaxing every ounce from his cock. When he was finally done he slumped back in the seat and took a deep breath.

I took in a deep breath myself. I hadn't even realized that I'd been holding it in.

"Good?" Kara smiled.

He looked over to her with a satisfied grin. "Oh yeah..."

While he pulled his pants back on, my sister pulled some wipes from the pocket behind the driver seat and began wiping off her cum covered tits.

'Oh shit...' I thought. 'Good thing I didn't put the camera in that side...'

They cleaned up and finished putting their clothes back on. Then the guy reached in his pocket and pulled something out.

'I KNEW IT!'

I watched as he pulled out a small wad of folded bills.

"Remember, it's double if I do it for you." Kara smiled.

He pulled a few bills from the stack and handed them to my sister. "Worth every penny!" he smiled.

"Thank you, sweetie! See you again soon?" she asked.

"Of course!"

Kara gave him a kiss on the cheek and then he let himself out. Once he was gone, Kara sat back in the seat and leaned her head back against the headrest. She spread her legs wide and continued to play with her pussy. I hadn't thought of it before but Kara hadn't cum at all that entire time. Apparently, she was making up for it now, though. I continued to watch for the next five or six minutes while my little sister got herself off, pushing a finger deep into her pink pussy over and over and bringing herself to a quick climax. When she was done, she pulled her shorts back up. She didn't look nearly satisfied but she collected her things and climbed out of her truck to head back into campus.

I turned off the camera and saved the recorded video to my tablet. I put the tablet away and sat for a moment, thinking to myself. I knew that she was up to something. I even had an idea what it was but I wasn't sure I could believe it. Even worse... I was still hard and I was horny as hell from watching my sister get paid for giving a handjob! I wondered to myself for a moment, 'What else is she getting paid to do?'

That night at dinner I couldn't make eye contact with her. She was still wearing the same outfit she had on that afternoon and it was impossible not to imagine her perky tits, covered in cum. The images from that afternoon replayed over and over in my head. I ate quickly and excused myself to go 'finish my homework'. Really, I just needed to get out of there and try to focus on something other than Kara. I had figured out what she was doing and even had a video to prove it. I could probably blackmail her for whatever I wanted. But what did I want? What was I going to do next?

The next day at school was a fog. I could hardly remember anything from my classes on Friday. I was just waiting. Waiting to see if my slutty sister was headed out to the parking lot again. To see if she was going to go out and give another masturbation show or handjob. I wasn't sure why I was thinking about it so much. I had the video after all. But I think I was more curious about what else she was doing with these guys. And although I wouldn't admit it to myself at the time, I think I really wanted to SEE what else she was doing with them.

Saturday, I went out with a few friends. Occupying my mind with something other than my sister gave it a break for a night. We hung out at my friend Sean's house, just a small group of us. I crashed there and had a lazy Sunday the next day. Eventually, Monday morning came and it was back to school again.

When lunchtime came, I walked out to my locker. I usually saw my sister leaving her class nearby, which was how I knew if she would be going out to her truck or not. That day she didn't.

Tuesday was the same. I guess she didn't have any kind of regular schedule with these guys. They probably just told her in the morning or something if they wanted to meet up.

Like every other eighteen-year-old girl, my sister was constantly on her phone, texting. It was like her phone was an extension of her body. All day and all evening she would text back and forth with people. Her friends I'm sure but probably guys as well. And that gave me an idea.

That night, I waited in my room until I heard the shower start in the bathroom I shared with Kara. I waited exactly sixty seconds to sneak into her room and find her phone, knowing that it was probably the only time of day it was ever left unattended. Just as I had hoped, it lay there on her bed. I picked it up and swiped the screen to unlock it. Jackpot.

I opened her text messages and scanned through the names of her recent contacts. The first few were friends of hers whose names I recognized. Then a bit further down was 'Matty'. The texts were a few days old but I opened it up and read through the conversation.

"See you at lunch!" was her last reply to him after he asked if she was available that day. That was on the Thursday I had watched them the previous week. Scanning through I saw where they had set up other dates previously over the last month or so. Backing out of that conversation, I looked through the names of other guys.

'Vbbbttttt' the phone vibrated in my hand, a new text displayed on the screen.

"New Message-Robbie: Free tomorrow?"

I could still hear the shower going so I knew that I still had a few minutes. I opened the text. There with the new message were their previous conversations. Again, I could see other dates where they had set up to meet at lunch. One text from him a few weeks earlier even asked "How much for a BJ?" to which Kara had replied "$100".

'Holy shit!' I thought. She WAS doing more than just handjobs. At least handjobs and blowjobs from what I read now. And charging $100 for one at that!

I scrolled down a bit more but stopped when I saw a photo she had sent to him. My eyes were glued to the small screen of the smartphone. I stood there for a few seconds and looked over the picture. It was Kara, of course, but she was topless and was squeezing her tits together with one hand while...