Chemistry Girl

Notes: Everyone in this story is 18 years old or above.

Mark could see Lisa's eyes focused on the bulge between his legs as she whispered, "Yeeeessss." He looked on as she shifted her eyes back up and locked onto his own. As he stared into her eyes, Mark could still taste Lisa's pussyjuice in his mouth, and it tasted like honey. The last pussy he licked and brought to orgasm was that of his on-and-off ex-girlfriend, Kendra Meers, a couple of days ago. Her pussy tasted slightly salty, but it was pink and so tight for his cock. Mark didn't have any complaints, and he liked her taste as well as the feeling of his cock being wrapped around by a wall of pulsing velvet. However, he had never licked her pussy with such abandon as when he was ravaging Lisa.

Taking a deep breath, Mark took in the scent of honey coming from her as he blinked before looking away from his sister's eyes to the half-open pizza box. He was certain the pie was already cold, and the toppings were most likely a solid mass of cheese, toppings, and bread. Groaning as he slowly sat up, he closed his eyes and slowly lifted both of his legs at the knees one at a time before he stood still for a few seconds, feeling his leg muscles flex and contract as they got used to taking his body weight once again after being on his knees for so long. Still, he limped as he turned towards his sister, who was looking up at him. Mark leaned down and kissed her sweat-covered forehead before he pulled his lips off her skin. Lisa pulled her head back until all he would have to do was lean down, and their lips would be pressed together.

He placed an arm past her left ear, his hand resting on the back of the couch just inches from her head. He placed his other hand gently on the back of Lisa's head, his palm gently pressing up into her damp hair. Their eyes were locked together, and this closeness to his sister had him feeling an intense desire once again.

He wanted to kiss her. And not kiss her like a brother should kiss a sister. Once he had this particular thought, he couldn't help but appreciate the irony. After all, he had just given his sister multiple orgasms over the course of two hours without a thought. Mark didn't laugh; he didn't want Lisa to get the wrong idea. He felt Lisa rest a hand on his cheek while another hand was resting on the bulge where his hardened cock was painfully pressed onto the inside of his thigh by his boxer briefs. He enjoyed the sensations going through his body as Lisa caressed the bulge.

As he stared into her eyes while leaning over her, Mark couldn't help but feel a heavy sense of desire once again. A sense of desire seemed to increase the more he leaned forward, their lips nearly touching. He kissed Kendra too; of course he did. He also fucked Kendra in her sister's room last week. But this was his sister. He was about to kiss his sister with the very lips that had been licking her pussy for the past two hours.

As Lisa continued to caress his bulge, Mark leaned forward and completed the connection between their lips. Nothing happened for a few seconds as their lips gingerly touched before they opened their mouths, and their tongues pressed against and licked each other. Mark heard Lisa moan into his mouth while he gently pressed his hand into the back of her head, their lips slowly being crushed together. They continued kissing for a few moments longer before parting their lips. Their eyes were on each other for a few seconds before he once again leaned forward and pressed his lips into Lisa's. They both moaned as intense passion took over, all thoughts of food and drink pushed aside while Mark reached down with his toned arms and slipped his hands under her thighs.

Lisa felt his hands slip beneath her thighs as she parted her lips and released a breath. Lisa was staring into his eyes and panting just as he was. There were no words spoken as Mark moved his hands up to the top of her thighs, where they met the curve of her ass. Lisa yelled and giggled when Mark squeezed her ass cheeks and picked her off the couch. She quickly wrapped her legs around his hips while he pulled her in, squishing her bare, soft, and sweat-sheened tits into his toned and hairless chest. She wrapped her arms around the back of his neck, their noses just a hair's breadth away from touching. She tasted the remains of her pussyjuice on his lips and tongue. It was a little salty, but she didn't mind. In fact, Lisa closed the tiny gap between their lips and kissed her brother once again. Mark returned the kiss with gusto as they moaned, their tongues dancing together.

Lisa pulled back with a bit of alarm when she felt Mark shift his weight and wondered if he was still feeling pain in his knees. 'Of course he is; he was on his knees for all this time.' Lisa smiled at the forced smile on Mark's face before telling her brother, "Put me down, Mark." She chuckled when Mark groaned out, "I can do this... All I have to do is carry you up the stairs and then to bed, and then..."

"You're in pain," Lisa chuckled before kissing him passionately once again for a few seconds and then pulling back, "put me down, and we'll both go upstairs side-by-side without you getting sprained knees." Mark chuckled before groaning once again as she unwrapped her legs, and he lowered her until her feet touched the carpeted floor. Lisa breathed in the musky scent coming from her brother. She could still smell the scent of strawberries in the air, mixed with the scent of his sweaty body.

Mark continued to stare into his sister's eyes; his hands were now on either side of her breasts, just under her armpits, as the last few hours raced past in his mind. Starting a few hours ago, from the moment Lisa left the shower, Mark felt as if there was something different about her. Something alluring. Something that seemed to be beckoning to him. It was unexplainable.

Mark forced his mind out of thoughts of the past and back to the present as he licked his lips, which had Lisa's saliva still on them, and he watched Lisa do the same to her lips with her tongue. Mark could feel sweat gathering on his forehead and the back of his neck. He leaned forward and kissed the left corner of Lisa's lips before kissing down to her chin. He heard her moan as he continued kissing up her jawline while both of his hands reached down her back and to her ass cheeks. Mark started to gently squeeze her luscious globes while kissing and sucking the skin just beneath her left ear.

"Goooooooooood!" Mark heard Lisa coo as she held down the back of his head with her right hand, and her left hand was caressing his bulge.

Between kisses and gently sucking her skin, Mark whispered, "You taste so good, sis. Just like honey." And it was true—her sweat tasted like honey. Just like her pussy juices.

As Mark continued his kisses down to Lisa's neck, he felt his heart thudding inside his chest as his mind wandered off to when he returned to his room after having finished taking a piss some hours ago. By then, Lisa had returned to her room and closed the door behind her. After he stepped into his own room, Mark closed the door and leaned back on it. Lisa was on his mind. He couldn't get the sight of her in the towel out of his mind. Already, Mark could feel his cock pressing against his pants. Quickly, he pulled down his trousers and his boxer briefs, breathing a sigh of relief as he did so. After being liberated from its prison, Mark looked down at his fully erect cock, all seven inches of it, standing at attention. In his mind, Lisa was starting to sway her hips from one side to another as if she were dancing sensually to a song only she could hear.

Mark grabbed his cock and started to slowly stroke while closing his eyes. In his imagination, Lisa had stopped swaying her hips and was standing just a few inches away. She was still in her towel as she looked down at his cock and then looked back up at him with the corners of her lips curved upwards into a gentle smile. Mark started to stroke his cock faster while grunting as his imaginary Lisa slowly got down to her knees, her mouth now a couple of inches away from his cock. He began to feel his balls swell with cum as he increased his stroke speed. He watched Lisa part her lips, her eyes looking up at him. Mark grunted while his body shook as bursts of cum shot out of his cock and landed on his carpeted floor, just before his imaginary Lisa could slip his cock into her mouth. "Fuck. Fuck. Fuck. Fuck," he whispered while struggling to keep down his voice since Lisa's room was just next to his. After he stopped cumming, Mark was panting hard when he received the message from Lisa that she was going to be taking a nap in the nude. All he could do was close his eyes and yell out, "Too much information." The entire time, his cock was still in his hand.

Mark pulled himself out of the memory and raised his head, lifting his lips from Lisa's skin. He heard Lisa groan out, "Don't stop." His eyes stared down at his sister, who still had her head tilted to one side to allow better access to her neck. Mark took in the scent of honey in the air. Even when he kissed her bandage a couple of hours ago, he could already smell the scent of honey. It was just a hint, nothing like this. And even with just a hint of that scent in the air, it felt as if it were intoxicating. He felt an urge going through his body—an urge that was greater than when he would be around Kendra. No, this feeling, this urge going through his body, was different than the times he kissed or fucked Kendra. From the moment he kissed the bandage, it felt as if something was reaching deep into his soul and pulling him towards his sister. This 'something' felt so animalistic and primal. It felt so natural.

His heart was racing as if it were going to smash through his ribs and run away, just like in the cartoons. As Lisa opened her eyes and tilted her head back to its usual position, Mark saw her looking back at him with a questioning expression on her face. Instead of saying something, Mark's mind went back to when he was between Lisa's legs; he remembered clenching his teeth together while pulling hard at the material covering Lisa's pussy with his thumbs and forefingers, grabbing the wet material. He remembered looking up at his sister and saying, "Lisa." She looked back down at him. Her face was covered in sweat. His mouth and nose were so close to the thin material covering her cunt. The soft material was stretched by his hands, pulling the section covering her pussy lips apart. The scent of honey continued wafting through his nose and down into his lungs. He wished there was a way he could smell this scent forever. He could feel the material starting to give way. Mark looked up to see her ample chest heaving up and down, and her lips parted as she panted hard. She licked her lips to moisten them just as the material ripped apart and her pussy lips were exposed.

Mark didn't wait. He knelt down and began kissing and licking her outer and inner pussy lips, as well as her clitoral region, before inserting his tongue as deeply as possible into her cunt. Mark could hear Lisa's screams and feel her body writhe. But he continued to lick up the sweat around her pussy as well as her pussy juices, which tasted as sweet as honey.

He pushed away thoughts of the past few hours and returned to the present once again. He reached down to the button that held his jeans tight around his waist. All he could think of was taking Lisa here and now. It consisted of turning her around, ripping off the remnants of her leggings, and then inserting his cock into her moist cunt. He wanted to fuck her. He wanted to thrust his cock into her. Mark looked on as Lisa moved her head down towards his unbuttoned jeans, then at the zipper he was pulling open. She looked back up at him. Lisa's lips parted as Mark just let his jeans fall down to the carpeted flooring before taking off his boxer briefs.

He heard Lisa gasp as she stared at his erect cock, now standing at attention after being freed from its cotton prison. Mark's only thought as she looked back down at the head of his cock, just brushing her abdomen, was to fuck her hard. He didn't want to make love to her. He wanted to hear her screaming while begging for his cock. He desperately needed her now. He needed her; he needed to thrust his cock into her hot cunt. And Mark was doing everything he could to hold back; he wanted to savour this moment. He wasn't sure why this sense of lust for his sister erupted today of all days, but whatever the cause, he was going to enjoy it.

Lisa was staring down at Mark's cock, her eyes lingering on the head and taking in its veiny length. This was the first time she had even seen a cock in person; after all, she had only heard some of the cheerleaders speaking about sucking off their so-called boy of the day. 'I bet some of them were just mouthing off,' she thought to herself as she slowly sat down on the couch once again while, at the same time, bringing a hand up to the shaft of his cock, just below the head, which was in her line of sight. Her hand hovered just inches above the foreskin, and her heart was racing as the scent of strawberries in the air continued to mix with the musky scent of Mark's sweat. Lisa was even able to feel the heat emanating from the shaft of his cock, and it felt incredible.

She needed to feel it in her hand. Slowly, one by one, her delicate fingers curled around the shaft, warm skin gently pressing against warm skin. She was breathing hard as she looked up at the expression of pressure on Mark's face as he gasped while closing his eyes. Lisa looked back down at her fingers around the sweaty shaft; her forefinger just barely brushed her thumb. She could feel the veins surrounding the shaft, and it felt both strange and incredibly hot.

"Stroke it," Mark gently said as he reached down and gently grabbed the hand wrapped around his cock. Lisa relaxed her arm and let Mark show her what she needed to do. It was not as if she hadn't heard about this from her friends, but actually stroking a cock in real life was something else. "Slowly," Mark whispered, his voice panting, as he let go of Lisa's hand, and she continued stroking his length. Her eyes were on the cock head, already slightly thicker than the shaft and pinkish in colour. She looked up at her brother, whose head was pulled back; she felt a sense of control, as if she were in charge of her brother's pleasure. Lisa's eyes returned to the cockhead, staring right back at her. She was still stroking—not too slow and not too fast. She could hear her brother moaning out, "Fuck, Lisa, sis, fuck." She wasn't sure what to do next. Lisa looked up at Mark, who still had his eyes closed while she stroked his shaft. Lisa couldn't help but mentally laugh; she would mentally brag, especially concerning Thompkins and what she wanted him to do to her, as well as what she wanted to do to him. But when it came down to it, she was as unsure as most virgins.

Just as she had that thought, Lisa felt a hand running through her damp hair. Looking back up, she smiled at Mark looking at her. There was a look of lust on his face as he said, "Use your tongue, sis. Lick under the head, around it, and then the... fuck." Lisa looked back down and could see some liquid coming out of the hole before she looked back up with a questioning look. "That's... fuck... that's precum... fuck..." Mark panted for a few seconds before saying, "Sis, open your mouth! Open your mouth!!" He then told her to stroke faster. He repeated it as if he were giving her an order. She quickened her stroking and opened her mouth as Mark held both sides of her head with both his hands.

"Close your eyes!" Mark yelled out before grunting out a "fuuuuuuuuckk.... Gooooood... fuuuuuuck!" Just as Lisa closed her eyes and as she further quickened her stroking, she felt something warm and wet splash on her nose, cheeks, lips, closed eyelids, and into her mouth. She could hear Mark growl out, "Fuck! Fuck!!! So goooood. Fuck!!! Fuck me, I'm cumming! Shit!!! Ooooh Fuuuuuuuck!!!! Cumming, I'm cumming!" It seemed as if minutes had passed by before Lisa stopped feeling cum splashing onto her skin. She was about to open her eyes while lifting her hand off Mark's cock so that she could wipe off the wetness on her face. She swirled the thick liquid in her mouth with her tongue. It was slightly salty, but she swallowed it.

"Wait," Mark panted. Lisa stopped, her hands nearly about to wipe off the cum on her face. She felt her brother's fingers gently wiping his cum off her eyelids as she lowered her arms, her hands now resting on the sides of his knees. "Open your eyes, sis," Mark gently said. Lisa opened her eyes to a look of absolute pleasure from Mark. He had a smile on his face before saying, "Wow! Fuck!!!" The corners of Lisa's lips curled upwards to form a smile while her hands gently rubbed the sides of his knees. After taking a gulp of air, Mark asked, "I came inside your mouth; did you swallow it?"

Lisa nodded her head as if swallowing cum was the most normal thing in the world. "It's a bit salty," she said as Mark ran both his hands through her thick, damp hair.

Mark muttered between breaths, "That's so hot. Hell, not even Kendra would swallow my cum." And it made Lisa proud of herself before she looked back at Mark's cock, which was angled lower after having released so much cum onto her face. She could still observe fluid dripping from the opening of his cock onto the carpet, and she could feel the cum on her face dripping down her cheeks, forehead, and nose. She wondered what she looked like; did she look like one of the pornstars on the videos she would stream when thinking about Thompkins? Did Thompkins even matter, especially after what happened with her brother so far?

Lisa pushed away thoughts of her chemistry teacher. She moved both of her hands around the front of Mark's knees and then slowly up his thighs. She could hear her brother moan as her hands slowly continued to move up until they reached his hips. Lisa parted her lips once again as she traced his toned muscles with her fingers. Mark hissed while taking a deep breath. Once her hands reached the base of his shaft, Lisa curled the fingers of her right hand around it. Lisa felt her brother's cock twitch slightly before starting to slowly stroke it while her other hand reached around and rested on his ass, much to Mark's surprise.

Lisa couldn't help but smile at the look of surprise on his face before she angled his cock towards her parted lips while still stroking him. Leaning forward, Lisa slowly slipped her full lips over his cockhead. Her tongue was slowly licking it, while her lips closed gently around his glans.

"Shit!!" Lisa heard Mark exclaim while she gently licked the glans of his cock, and at the same time she stroked his shaft. She could feel his cock becoming harder once again. Lisa could taste the remnants of his cum around the opening of his glans by licking the sensitive tissue's tip and base. She wanted more. Fuck, she needed more. Lisa hummed as she slid more of his cock into her mouth. "Ahhhhhhhh!!!" Mark groaned out as she quickened her stroking while taking even more of her brother inside her warm and wet mouth. Every time she took in more of his cock, she would pull her head back until only his glans were in her mouth, caressing the underside of his cock with her tongue. Lisa could feel her spit on his shaft, lubricating her hands as she continued stroking it. She would run her tongue around the glans before taking most of his length, at least just before reaching the back of her throat, and then repeat. Doing so released more of her saliva on his shaft, resulting in more lubrication. In the back of her mind, though, she thought it odd that her gag reflex wasn't activating. She would even gag when brushing the teeth in the back of her mouth, but this time she was taking in nearly the full length of a cock, but Lisa did not feel as if she needed to gag.