The Forbidden Equation

Shin Yuna paced the empty corridors of Evergreen College's social sciences building, her heart pounding like a drum in her chest. It was late afternoon on a Friday in September 2025, and the campus was starting to wind down for the weekend. Students hurried past with backpacks slung over their shoulders, eager for parties or study breaks, but Yuna had no such luxury. Her mind was fixed on one thing: Professor Joseph Park's advanced statistics class. She was failing—badly. Her latest quiz score was a pathetic 48%, and if she didn't turn things around, her dreams of graduating with honors and landing that internship at the psychology research firm would evaporate like morning dew.

Yuna was 21, a junior majoring in psychology, with a sharp mind for human behavior but a complete aversion to numbers. She'd immigrated from South Korea as a teen, and while her English was flawless and her social skills impeccable, math had always been her nemesis. Professor Park, however, was a different story. He was 31, Korean-American like her, with a reputation for being both brilliant and unyielding. Tall and lean, with broad shoulders from his weekend gym routines, he had piercing dark eyes, a chiseled jaw, and hair that was always perfectly combed back with just a hint of product. His lectures were intense, his grading merciless, but Yuna had caught him staring at her more than once—those lingering glances during class discussions when she'd raise her hand, her short skirts riding up just a bit as she shifted in her seat.

She'd dressed strategically today: a tight black miniskirt that hugged her hips, a low-cut white blouse that showed a tease of lace bra underneath, and thigh-high stockings that accentuated her toned legs. Her long black hair was loose, framing her heart-shaped face and full lips painted a subtle red. If studying wouldn't save her grade, perhaps persuasion would. It was a risky plan, but desperation bred boldness.

The lecture hall was empty when she slipped back in after class had ended. The room was spacious, with tiered rows of desks ascending toward the back, a massive whiteboard covered in scribbled equations, and a podium at the front with a projector screen hanging above it. The air smelled of chalk dust and faint coffee from the morning sessions. Joseph was at the front, packing his leather briefcase, his button-down shirt sleeves rolled up to reveal muscled forearms.

"Professor Park?" Yuna called out, her voice echoing slightly as she descended the steps. She put a sway in her hips, her heels clicking on the linoleum floor.

He looked up, adjusting his wire-rimmed glasses. "Yuna. I thought everyone had left. What is it?"

She stopped a few feet away, leaning casually against one of the front-row desks, crossing her arms to push up her cleavage just a touch. "I wanted to talk about my grade. It's... not where I want it to be. I'm really worried about failing."

Joseph sighed, snapping his briefcase shut. He knew her type—smart but lazy with the technical stuff. But she was engaging in class, always contributing thoughtful points on behavioral data. And yes, he'd noticed her physically: the way her skirt hugged her ass, the curve of her breasts under those thin blouses. He pushed the thought away; he was a professional. "You've missed a few assignments, and your test scores reflect that. Have you considered tutoring?"

"I have," she said, stepping closer, her perfume—a mix of vanilla and jasmine—wafting toward him. "But I think I need something more... hands-on. Maybe from you directly?"

His brow furrowed, but there was a spark in his eyes. "My office hours are posted. You can come by then for help."

Yuna bit her lip, tilting her head with a flirty smile. "What if we did it now? The building's pretty quiet. I promise I won't take up too much of your time... unless you want me to."

Joseph paused, his gaze dropping to her lips for a moment before snapping back up. "That's not appropriate, Yuna."

"Oh, come on, Joseph," she purred, using his first name deliberately, her hand lightly brushing his arm. "We're both adults. And I see the way you look at me in class. Like you're imagining what I'd look like without all these equations between us."

Bold. Too bold. He should end this now, but the hallway outside was empty, and a forbidden thrill stirred in him. He'd been divorced for two years, buried in work, and celibate for months. "You're treading on thin ice."

She leaned in, her breath warm against his ear. "Maybe I like the risk. What if I could persuade you to bump my grade? Show you how grateful I can be?"

His resolve cracked. Grabbing her wrist—not gently—he pulled her toward the door. "My office. Now. But if we're doing this, it's on my terms."

Yuna's pulse raced with excitement and nerves as she followed him down the dimly lit hall, past locked classrooms and bulletin boards advertising club meetings. His office was at the end, a plaque reading "Dr. Joseph Park, PhD" on the door. He unlocked it, ushering her inside and locking it behind them with a decisive click that sent a shiver down her spine.

The office was intimate: a large oak desk piled with graded papers and a laptop, bookshelves crammed with textbooks on statistics and data science, a leather armchair in the corner, and a small window overlooking the quad with blinds partially drawn. The room smelled of old books and his cologne—woody and masculine, mingling with the faint metallic tang of the air conditioning.

"Sit," he said, pointing to the visitor chair, his voice low and commanding.

Instead, Yuna perched on the edge of his desk, crossing her legs seductively, her skirt riding up to reveal more of her smooth thighs. "I'd rather be closer. So, Joseph... how can I convince you?"

He stepped forward, towering over her, his hands planting on either side of her on the desk, caging her in like prey. His eyes darkened with lust, the professional facade crumbling. "You think flirting will get you a passing grade? It's going to take more than that, little tease."

She reached up, her fingers loosening his tie with a mischievous grin, her nails grazing his skin. "Then let me show you more. I can be very... dedicated. What do you want me to do, Professor? Beg?"

That was the breaking point. Joseph's hands shot to her waist, yanking her against him roughly, his fingers digging into her hips hard enough to leave bruises. He claimed her mouth in a bruising kiss, his lips demanding and unforgiving, tongue forcing its way past her teeth to tangle with hers. Yuna moaned into it, the taste of his coffee-laced breath mixing with her cherry lip gloss, sweet and bitter colliding. Her arms wrapped around his neck, pressing her soft body flush against his hard one, feeling the heat radiating from him like a furnace.

"Fuck, you've been teasing me all semester with those short skirts and those innocent little smiles," he growled against her neck, his teeth sinking into the sensitive flesh, sucking hard to draw blood to the surface, marking her as his. The sting shot straight to her core, making her thighs clench.

"Guilty as charged," she whispered back, her voice breathy and flirty, even as she gasped from the pain-pleasure. "But admit it, Joseph—you've been hard for me in class, haven't you? Imagining bending me over your desk just like this."

He spun her around with brutal force, bending her over the desk so her chest slammed against the cool, polished oak. Papers scattered like leaves in a storm, fluttering to the floor, and a pen rolled off the edge with a clatter. "You have no fucking idea how many times I've wanted to rip that skirt off and fuck the laziness out of you." His hands hiked up her miniskirt, bunching it around her waist, exposing her lace thong that barely covered her glistening pussy. The air hit her skin, cool and raising goosebumps, contrasting with the heat building between her legs.

He spanked her ass sharply, the crack echoing off the bookshelves like a gunshot, her flesh jiggling under the impact. Yuna yelped, the burn spreading like wildfire, but it melted into a deep ache that made her wetter. "Yes... punish me, Joseph. I've been such a bad student," she teased, wiggling her ass back against him, feeling his erection press against her through his slacks.

"Bad? You're a fucking disaster in my class," he snarled, spanking her again, harder this time, his palm leaving a red handprint on her olive skin. Then again, and again, the rhythm relentless, each slap sending jolts of electricity through her body. Her thong was soaked now, the fabric sticking to her folds. "But look at you, dripping like a slut. You love this, don't you?"

"Only when it's you spanking me," she moaned, her cheek pressed to the desk, the wood smooth and unyielding under her. "Harder, Professor. Make it hurt so I remember to study next time."

Joseph chuckled darkly, his fingers hooking into her thong and yanking it down her legs with a rip of fabric, the lace tearing slightly. He kicked her feet apart wider, exposing her completely, the office air teasing her wet entrance. Without warning, he plunged two fingers inside her, rough and deep, the intrusion making her cry out as her walls stretched around him. The slick sounds of her arousal filled the room, obscene and loud, as he pumped them in and out viciously, curling to scrape against that sensitive spot inside her.

"Fuck, you're tight and soaking," he groaned, his free hand spanking her again while he finger-fucked her. The dual sensations—sting and fullness—had her toes curling in her heels. "This pussy's been waiting for me, hasn't it? Begging to be filled."

"Yes, oh god, yes," Yuna whimpered, her hips bucking back against his hand, chasing more. "Finger me harder, Joseph. Make me cum on your desk like the failing whore I am."

He added a third finger, stretching her further, the burn exquisite as he thrust faster, his thumb pressing hard on her clit, rubbing in rough circles that made stars explode behind her eyes. The desk creaked under her weight, the laptop shifting slightly from the vibrations. Sweat beaded on her forehead, mixing with the scent of her arousal that hung heavy in the air.

But just as she teetered on the edge, he pulled his fingers out abruptly, leaving her empty and throbbing. "Not yet, tease. You don't cum until I say." He brought his slick fingers to her lips. "Suck them clean."

Yuna obeyed, turning her head to take them into her mouth, tasting herself—salty and musky—sucking hard while maintaining eye contact, her tongue swirling around them like she would his cock. "Mmm, I taste good, don't I? But I'd rather taste you."

Joseph's eyes flashed with hunger. "On your knees, then. Show me how badly you want that grade."

She dropped to the carpeted floor, her knees sinking into the rough weave, ignoring the burn as she unbuckled his belt with frantic hands. His slacks fell, and she freed his cock—thick, veined, the head angry red and leaking pre-cum. It throbbed in her hand, hot and heavy. Yuna licked her lips, then took him deep, her throat relaxing to accommodate his size.

"Fuck, that's it," he groaned, his hand fisting her long hair, yanking her forward until her nose pressed against his abdomen. He held her there, her gag reflex kicking in, tears streaming down her cheeks as she choked. "Choke on my cock, Yuna. Earn every fucking point."

She pulled back for air, gasping, strings of saliva connecting her lips to him, then dove back in, bobbing roughly, her hands cupping his balls, squeezing gently. The office filled with wet slurping sounds, her moans vibrating around him. Joseph thrust into her mouth, face-fucking her with no mercy, his hips snapping forward.

"Good girl... but you're still failing at deepthroating," he teased harshly, pulling her hair tighter. "Deeper, slut. Or no A for you."

Yuna pushed herself, taking him all, her throat burning, but the degradation only fueled her arousal. When he finally pulled out, strings of spit dripping down her chin, he hauled her up by the arms, slamming her back onto the desk.

He ripped open her blouse completely now, the remaining buttons flying across the room, pinging off the bookshelf. Her bra was next—yanked down roughly, exposing her breasts to the cool air, nipples pebbling instantly. Joseph latched onto one, sucking hard enough to bruise, his teeth grazing the sensitive bud while his hand twisted the other nipple viciously.

"Ah! Joseph, bite me harder," she begged, her back arching off the desk, the wood digging into her spine. "Mark my tits so I can't forget this lesson."

He obliged, biting down until she screamed, the pain shooting straight to her clit. Then, spreading her legs wide with his knees, he aligned his cock and slammed into her in one brutal thrust, burying himself to the hilt.

Yuna's scream echoed off the walls, the sudden fullness splitting her open, her walls clenching around his thickness. "Fuck! You're tearing me apart..."

"Take it, you teasing bitch," he grunted, pulling almost all the way out before ramming back in, the force shaking the desk, a stack of books toppling from the shelf behind them with a thud. His hands gripped her thighs, nails digging in, leaving crescent marks as he pounded her relentlessly, each thrust deeper, harder, the slap of skin on skin mingling with her slick wetness.

"Yes, fuck my failing pussy raw," she moaned, her nails raking down his arms through his shirt, drawing blood. "Ruin me, Professor. Make me your cumdump for that passing grade."

He leaned down, capturing her lips in another savage kiss, biting her lower lip until it bled slightly, the copper taste mixing with their saliva. His pace was punishing, hips pistoning like a machine, hitting her cervix with every brutal entry. The office air grew thick with the scent of sweat and sex, the window fogging slightly from their heated breaths.

Joseph flipped her over without warning, her breasts pressing painfully against the desk's edge as he re-entered from behind, even deeper now. "Arch your back, slut. Show me that ass."

She did, pushing back against him, the new angle making her see stars. He spanked her repeatedly—left cheek, right, the burns overlapping until her skin was on fire. "This ass is mine now. Every time you sit in my class, you'll feel this."

"Fuck yes, own it," she cried, her voice hoarse. "Spank me until I can't sit straight."

His hand came down like thunder, the pain blending into ecstasy as he fucked her harder, one hand wrapping around her throat from behind, squeezing just enough to make her lightheaded, stars dancing in her vision. The chokehold heightened everything—the slide of his cock, the burn of her ass, the ache in her core.

They moved to the floor next, the carpet rough against her knees as he positioned her on all fours. "Crawl for me, tease. Beg like a dog."

Yuna crawled a few steps, humiliated but aroused, her pussy dripping down her thighs. "Please, Joseph... fuck me like an animal. I need it."

He mounted her from behind, slamming in with animalistic force, his balls slapping her clit. The floorboards creaked under them, dust motes swirling in the air. He pulled her hair like reins, yanking her head back, exposing her throat for more bites.

"You're clenching so tight... gonna cum already?" he taunted, his free hand reaching under to pinch her clit hard.

"Yes! Fuck, make me cum," she pleaded.

He did, rubbing her clit roughly until she shattered, her orgasm ripping through her like a storm, juices squirting onto the carpet. But he didn't stop, fucking her through it, prolonging the waves until she was sobbing.

Finally, he pulled out, flipping her onto her back on the floor and straddling her chest. "Open your mouth."

She did, and he thrust into her throat one last time before pulling out to cum, hot ropes splattering across her face and breasts, marking her completely. The salty taste lingered as some landed on her tongue.

Panting, Joseph looked down at her, spent but not done. "Clean up. We're moving to the classroom. I want to fuck you everywhere you've failed."

Yuna wiped her face with her torn blouse, her body trembling but eager. "Lead the way, Professor. I'm not done earning that A."

They slipped back into the lecture hall, the door locking with a heavy thud. The room was bathed in the golden hues of sunset filtering through the high windows, casting long shadows across the tiered desks. The air was cooler here, carrying the faint echo of chalk and eraser dust, but soon it would reek of them.

Joseph pushed her against the podium roughly, the wood digging into her lower back. "Bend over it, hands gripping the edges. Spread those legs wide."

She complied, her skirt still bunched up, ass exposed and red from earlier. He dropped to his knees behind her, spreading her cheeks and diving in with his tongue, lapping at her pussy like a starving man. The wet sounds were amplified in the vast room, his tongue flicking her clit before plunging inside her.

"Oh fuck, Joseph... eat me out on your podium," she moaned, her knuckles white on the wood. "Taste how wet you make me."

He sucked her clit hard, biting gently, making her buck. "You taste like failure and desperation. Delicious." His fingers joined, thrusting while he tongued her ass, the taboo sensation making her gasp.

Rising, he aligned and thrust in, the podium shaking violently, the microphone stand rattling as if amplifying their sins. "Imagine lecturing tomorrow with your cum stains here," he growled, pounding her, each thrust echoing like a lecture point.

"Yes... fuck me where everyone watches," she teased, pushing back. "Make the whole class smell like us."

He spanked her ass, the cracks resounding through the hall. "Dirty little student. You'd like that, wouldn't you? Getting railed in front of them."

Pulling out, he sat in a front-row chair, pulling her onto his lap in reverse cowgirl. "Ride me hard. Bounce that ass."

Yuna slammed down, the chair creaking dangerously, her breasts bouncing as she ground against him. His hands gripped her hips, slamming her down harder, bruising her further. "Faster, slut. Work for that grade."

"I'm riding you like a pro, aren't I?" she panted, teasing even as sweat dripped down her back. "Bet no other student fucks like this."

He stood abruptly, lifting her with him, her legs wrapping around his waist as he fucked her standing, using the seat backs for leverage. The tiered rows loomed, empty but judgmental. "None as tight as you."

They moved to the demonstration table, long and sturdy. He laid her on it, legs over his shoulders, folding her in half as he hammered down, the table groaning, equations on the whiteboard blurring from the vibrations.

"Deep... so fucking deep," she cried, her nails scratching the table. "Split me open, Joseph."

He did, thrusting with all his strength, his balls slapping her ass. Then flipped her to her stomach, ass up, and took her doggy style, pulling her hair to arch her back painfully.

"Take it all, you greedy bitch," he grunted, spanking between thrusts.

Against the whiteboard next—her breasts smearing ink, the dry-erase dust coating her skin like powder. He fucked her from behind, one hand choking her, the other fingering her clit.

"Cum again," he demanded.

She did, screaming, her body convulsing as ink transferred to her sweat-slicked skin.

Back to the podium for the finale: her on knees, sucking him rough, throat fucked until he came down her throat, forcing her to swallow every drop.

But even then, they weren't done. Returning to the office, they collapsed onto the couch, her straddling him for another round. He fucked her sideways, then missionary with legs pinned, then anal—slow at first, then rough, her cries filling the room.

"Take it in your ass, tease," he growled, thrusting hard.

"Yes... fuck my ass for extra credit," she moaned.

Multiple orgasms later, positions blurring—standing against the door, floor again—they finally collapsed, bodies entwined, the rooms in ruins.

"You pass with flying colors," he said, smirking.

Yuna grinned, cum-streaked and satisfied. "Best lesson ever."