Fic already posted on Archive of Our Own. Thanks to CTR69 for helping with the intro.

"Thank you... How about a hug?" Penny sweetly asked, stretching her arms.

"How about a hearty hand shake?" Sheldon replied with his usual nonchalance.

"Come on" she ignored his request and stepped forward.

She hugged him dearly, not wanting to let him go, and snuggled into his taller frame, her head resting on his chest. Him being almost a foot taller always provided her with a sense of comfort and security.

She smiled and tightened her grip. No matter how different they were and how this often caused little fights like the one they just had, in the end they always found a constructive way to communicate. He got more comfortable and wrapped his arms around her, his palms now laying on her back.

Her smile faded soon, replaced by quiet sobs. "Sheldon... I miss him" She barely contained her tears. Sheldon looked into her eyes and gently wiped the tears under her eyes. Penny raised up on her toes and froze an inch off his lips. They both felt attraction and electricity in the air, now so close to being finally uncovered after all those years of denial.

"Sweetie, we can't..." Penny looked away and sobbed again, feeling his fingers caressing her cheek.

Sheldon didn't say anything, he just leaned in and kissed her. He propped up her chin and gently nibbled her upper lip. Penny slowly let go her hug and brought her hands up onto his shoulders.

"We shouldn't be doing this" Penny whispered, but kissed him again. This time with more tongue. "It's wrong… mmmff..." It had been roughly two years since she last kissed someone who wasn't Leonard. She was amazed by how Sheldon was so skilled, being someone who claimed all the time his reject for physical contact.

Sheldon pulled away a little and looked at her blushed face. "I didn't tell you to stop. I need you..." Penny was getting turned on. She's been left for so long without, she couldn't take it anymore. Her hand reached between their bodies and over his crotch.

Conflicting thoughts ran through his mind. Even if he didn't know much about social rules, he was sure hooking up with his best friend's girlfriend was something not to be done. At the same time, though, she always made him feel something nobody else aroused in him, that he had never been able to explain with an equation. Also, he promised Leonard he would have taken care of her and, at the moment, she really needed to be comforted. He played his last card to see if this tension could be solved differently.

"I can make you another hot beverage. Leonard..."

"Ssshhhh, he's not here. I want you tonight. You did make a promise, right?" Penny looked up at him again and slid her hand up and down across his pants. Feeling him getting harder under her touch.

At this point he let himself go, his thoughts not conflicting at all anymore. "I did" he said, gently grabbing her arm and pulling it away from him. His right hand slowly traced a path through her flank and landed at the top of her trousers. He unzipped them and slid his fingers under her panties.

"Yes Sheldon, go on... Uh, oh, yes, um..." she moaned in pleasure when she felt his thumb circling her labia.
His lips were now planting soft, seducing kisses on the side of her neck while his hand worked to trigger nerves all around her pelvis.

"Yeeees... Uh, sweetie, this feels so good" she whispered, when his index slid in her hole deep inside. Sheldon fingered her pussy very slowly, thumb on the outside, index on the inside, rubbing her clit. He leaned towards her and pressed his lips to hers again. This time their kiss was more fierce, mouths slightly open to brush the other's tongue tip with their own. Her right hand went to his face, holding him still.

"Fuck!" she screamed, breaking the kiss. His fingering technique was so scientific she almost came with their clothes still on.
"I need more... I need you, sweetie. Please, take care of me" she whimpered.

She took the lead and grabbed his arm, walking both into his bedroom. Penny made him sit on the border of the bed, while she took her sandals off and sat on his lap, facing him. As soon as she did so, Sheldon abruptly embraced her body and flipped her, pressing her back to the mattress and taking back the lead.

"I said I'm gonna take care of you" he growled.

"Oh... We are horny, doctor Cooper, aren't we?" she seduced him, trying to turn him on even more.

"You just used grammar correctly, you can say it loud" he replied, remaining very serious.

He pressed another deep, passionate kiss on her mouth, before his lips attacked her neck again. She closed her eyes and enjoyed the feeling of his tongue on her chin, leaving a hot trace of saliva on her face.

"Let me take it off" he said, grabbing her dress and lifting it up above her head. She sat for a moment to help him take her multicolor dress off. He then reached behind her back and removed her light blue bra as well.

Sheldon squeezed her round breasts and pushed her on her back again. His determined, dominating behavior was turning her on more and more every ticking second.
He lapped her nipples and took them between his teeth, before sucking on her whole size. Penny bit her lower lip and moaned.

He kept licking her body very slowly, around the navel and very close to her pelvis. She still had her trousers on but, before removing them, she wanted him to have her feet. She raised her left leg and pressed her sole against his face, suddenly interrupting his methodic system. He gave it a quick kiss but immediately grabbed her leg and lowered it.

"Excuse me? I am supposed to take care of you. This means, we're doing it my way" he stated. She proudly giggled for having got exactly the reaction she wanted.

"Mmm... Show me your way, sweetie. I'm all yours tonight"

Sheldon lowered her already unzipped black trousers and removed them, admiring her inviting flesh barely covered by her panties. Penny kept her eyes closed as he slid his fingers inside once again. He managed to get so deep and so fast, it was like they were already fucking.

"Umpf... Ugh... Yes, sweetie, kept going... Urgh" His pace fastened, rubbing her burning walls and sending her off. He lowered her panties just a bit, enough for his tongue to join the party.

She wrapped her legs behind his neck as her pussy was now being double penetrated. He kept using his refined scientific techniques, easily switching between licking and sucking while his index and middle finger did the rest.
Soon enough, she squirted on his face, drenching her panties as well. She stretched her legs and laid there for a while, trying to catch her breath.

Unlike her, Sheldon wasn't tired at all. Her soaked pussy was tastier than a steak, but his cock still wasn't fully erected.
When she gained some energy back, she sat up and took off her wet panties, leaving herself completely naked.
She reached his face and kissed him deeply, sharing with him the taste of her juices.

"OK Sheldon,you took care of me enough. Now it's my turn" she exclaimed. Together they removed his t-shirts, throwing them on the pile of clothes formed on the floor. He let her lead, after all she was the one who needed comfort. Also, he knew he would re-take control over her soon.
Penny massaged his amazingly built chest with her left hand and kissed his nipples, while her right grabbed his hardening bulge, giving it a good squeeze.

"On your back, Sheldon" she commanded. He lied down as she unbuttoned his trousers and lowered them, leaving his erect cock out in the air.
"Um... It looks so tasty" she exclaimed, in her very seductive tone.
She gave a few licks on his balls and across his length to the tip but didn't take him in her mouth, right now she just wanted to have a good fuck.

She climbed upon him in cowgirl position as his whole length fitted inside her wet channel.
"Uh... So big... Uh" she murmured. She began to bounce on him, starting slowly then increasing her pace. Being so wet, she easily managed to take him whole with each thrust.
She closed her eyes again and grabbed her boobs, enjoying this sensation she had missed for quite a while now. Actually it had been just two months since she last had it with Leonard, but her big ol' five nature couldn't resist for another two. In fact, she thought, it was quite a miracle she didn't do this earlier.

The room was now filled with the noise of the creaking bed and of his cock slapping deep inside her vagina every time her ass bounced on his legs. Everything was so erotic and obscene to bring her on the edge of another orgasm. She leaned towards him, kissing him passionately as she came again, moaning loudly into his mouth.

Her face was flushed, but she definitely didn't have enough. She climbed off him and removed his trousers, underwear and socks in one fluid movement, leaving him buck naked.

"I need you to take care of me again" she whispered, smiling at him. She laid on her back once more and spread her legs while he kneeled in front of her and started rubbing her labia with the tip of his cock, playing with her exactly like he did before with his hand.

"Mmm... That's so fucking good. Keep it like that"

He managed to last very long. She had already come twice while he didn't even have any precum, despite having been roughly fucked. He slowly slid his length inside her from above while she rested her right ankle on his shoulder. He wrapped his arm around her calf and sped up, trying to hit every sensitive spot inside her spasming drenched pussy. A thick line of sweat formed on his forehead, now he was pounding into her with every muscle in his crotch, almost hitting her cervix with every noisy thrust.

"Oh my gawd... Ooooh, mmm, yes baby... Urgh" Penny was once again losing her mind, and it felt like he was also giving up on his precise mathematical method to just enjoy this wild night with his roommate's girlfriend.
He let go of her leg and she took the moment to lock it behind his back as she felt her third orgasm approaching. She tossed her head back, eyes rolling upwards, and let out a wild scream.

Sheldon slowly pulled off her, with a bit of precum on his tip. He still had to cum but he was finally starting to feel tired.

"Shit, how can you last this long?" she asked while breathing hard, shocked by his impressive resistance.

"I always do my best in everything I do. This includes taking care of you" he simply stated.

"Awww... Come here, honey" she brightly smiled, pulling his head down and kissing him deeply. Their eyes closed and their naked sweaty bodies clinged to one another as they ate each other's mouth. Their tongues danced together and explored the other's, lips sucking passionately, her hands caressing his hair.
They made out like teenagers in love for several minutes, sucking on each other's tongue every time they briefly pulled apart to catch their breath, before starting all over again.

His dick was growing, he could feel his tip pressing against her pubes.
"Turn around" he quietly ordered, after breaking the kiss.
She stood on her knees and bent her body forward, resting her forearms on the mattress. He kneeled behind her magnificent ass, stroked his fat cock bringing it to the maximum size and positioned it again inside her pussy.
From this angle he could reach every spot inside her tunnel, including those few left unexplored. He caressed her belly and started moving his hips inside her, going very slowly at first then gradually speeding up.

"Yes sweetie, oh my gawd, so fucking good" Penny was already picturing in her mind what would have happened soon. She was looking forward to feel his hot load flowing inside her body like a flooding river.

Her ass cheeks bounced in rhythm with his restless thrusts, slapping against his pelvis as she moved her hips backwards, trying to match his rhythm to take him even deeper. They both groaned like Neanderthals when he hugged her body and pulled her towards him, pressing her back to his chest and thrusting his hips as deep inside as humanly possible. His long cock scorched her whole spasming wet tunnel, filling her up to the cervix, stimulating myriads of nerves all across her lower abdomen. He kneaded her boobs in his hands and eagerly kissed her upper back.

The bed was shaking so violently she would have thought it was going to break, had she been able to think at this point.
He let go of her breasts and grabbed her head to turn her face around for another hot kiss, slipping his tongue in her mouth. The mutual pleasure and satisfaction they were giving each other was borderline hypnotizing them. Even his genius mind wasn't thinking about anything, his bedroom was the only existing universe right now.

His balls started spasming, he knew he was finally so close. He slammed into her one last time and raised his pelvis, while she backed up against him taking all his length inside her just in the moment he released his load.
His first shots pumped her cervix full with hot sticky cum, almost directly reaching her hungry womb. They both growled loudly, their animalistic vocalizations echoing all across the upper half of the building, probably waking up whoever was sleeping.
As he kept spurting more streams invaded her, covering every inch of her wet insides. He pulled off, a bit of extra cum dripping out on her thighs, and collapsed on his back.

Penny looked back, completely ecstatic, and noticed he was still semi hard.
"Damn you, how the hell is that possible?" she exclaimed just before jumping between his legs facing him. She was so tired but there was this last thing left to do, she couldn't stop now. She dived her mouth into his cock and sucked it like an icicle, liking him clean, then took him in the depth of her throat.

He didn't move at all, he had been the dominating one almost all the session and was extremely satisfied of his job. He just watched her beautiful face getting fully penetrated, her hands firmly holding his root, until he came again. The second load wasn't as hard and plentiful as the first, but still enough for her to enjoy his tasty semen splashing her throat.
She swallowed every drop of his fluid, licking her lips off the few shots that hadn't reached her digestive system.

Penny finally let go of him and collapsed on his right. She felt so pleased to have both her upper and lower belly completely filled with his seed.
Both of them knew they needed a shower, but they just didn't have enough strength. They simply covered their naked bodies with the sheets and cuddled.

"You know... Leonard won't be back for two months..."

"In two months" despite being half asleep, he still managed to correct her, which made her smile.

"Anyway... I'll definitely need you to take care of me again"

"And I'm definitely willing to do so" he said, watching her wonderful face and kissing her nose.

They closed their eyes and quickly fell asleep, naked in each other's arms.