The chemistry laboratory on the third floor of Shanghai Imperial University was quiet in the late afternoon. Sunlight filtered through the large windows, casting long shadows across the rows of wooden benches, glass beakers, and Bunsen burners. The faint smell of chemicals lingered in the air, mixing with the subtle scent of perfume and young skin.
Lin Xia stood at the front bench, wearing her usual university uniform — a crisp white blouse that hugged her slender frame and a short pleated skirt that showed off her insanely long, smooth legs. Her perky C-cup breasts pressed gently against the fabric, and her long black hair fell straight down her back. She looked every bit the innocent campus goddess, but today her cheeks were slightly flushed as she tried to complete the practical experiment.
Principal Wang stood behind her, watching closely. The fat, bald 58-year-old chemistry teacher (and principal) had a greedy smile on his face. His small eyes roamed over Lin Xia's body without shame — especially the way her short skirt rode up slightly when she leaned over the bench.
"You failed the titration again, Lin Xia," he said in a low, authoritative voice. "The color change was completely wrong. The whole class saw it."
Lin Xia bit her lip, looking down. "I'm sorry, Principal Wang…"
He turned to the rest of the students. "Everyone else, pack up and go to your next class. Lin Xia will stay and redo the practical properly. I'll supervise her personally."
The other students quickly gathered their things and left, whispering among themselves. Within a minute, the laboratory door clicked shut, leaving only Lin Xia and the principal alone in the large room.
Principal Wang stepped closer behind her. His fat belly brushed against her back as he leaned in. "Now that we're alone… let's continue the lesson properly."
His hand slid down and pinched her plump little ass cheek hard through the short skirt.
"Ah…" Lin Xia gasped softly, but she didn't pull away.
"Focus on the experiment," he whispered, his voice thick. "But keep that pretty ass still for me."
He pressed his crotch against her ass and started humping slowly, grinding his hardening cock against her skirt. The fat bulge rubbed up and down between her cheeks while he pretended to point at the beaker.
"See how the solution needs to be mixed gently?" he said, voice casual but breathing heavier. "Just like I'm mixing against your ass right now…"
Lin Xia's long legs trembled. She pushed her ass back against him slightly, responding to his dirty humping. "Principal Wang… your cock feels so hard against my ass… it's rubbing right between my cheeks…"
"Good girl," he groaned quietly. "Keep talking like that while we do the practical. Tell me how it feels."
He kept grinding, his hands resting on her slender waist as he dry-humped her from behind. The short skirt rode higher with every thrust.
"Pull your skirt up a little," he ordered.
Lin Xia obeyed, lifting the pleated skirt to expose her white panties. Principal Wang immediately hooked his fingers into the waistband and slowly dragged the panties down her long legs. He left them around her ankles for a moment before pulling them completely off and spreading them open on the bench in front of her.
"Look at this," he said, holding the panties up. The crotch was visibly wet. "Your panties are soaked, Lin Xia. In chemistry terms, that means your body produced a lot of natural lubrication. See how sticky and shiny it is? That's your pussy getting excited for an old man's cock."
Lin Xia's face burned with shame and arousal. "Yes, Principal… my panties are so wet because of you… my pussy keeps leaking while you hump me…"
He spread her across the lab bench, bending her forward so her perky C-cup breasts pressed against the cool wood and her long legs were spread wide. Her bare pussy and tight little ass were now completely exposed.
"Stay like this," he commanded. "We're still doing the practical."
He reached for a round, flat laboratory stool — the kind with no backrest, just a simple circular seat. He pulled it behind Lin Xia and made her sit backward on it, facing away from the bench. Her long legs straddled the stool, and because she was sitting backward, anyone looking from behind would have a clear view of her spread pussy and ass.
"Perfect position for the next part of the lesson," he said, standing behind her. One hand reached around and pinched her nipple through the thin blouse. "Feel that? Your nipple is so hard already."
Lin Xia moaned softly. "Ah… Principal Wang… you're pinching my nipple so hard… it feels sensitive…"
While still "teaching," he kept one hand on her breast, rolling and pinching the stiff nipple through the fabric. His other hand picked up a clean glass test tube from the rack — long, smooth, and rounded at the end.
He rubbed the cool glass tube against her wet pussy lips first, teasing her clit in slow circles. "This is like a practical demonstration of insertion technique," he said casually. "See how wet you are? The tube slides so easily…"
Lin Xia's breathing quickened. "Yes… the test tube feels cold against my pussy… please… push it in…"
Principal Wang slowly pushed the rounded end of the test tube into her tight pussy. Inch by inch the glass disappeared inside her, stretching her pink walls while he continued pinching her nipple.
"Tell me how it feels," he ordered.
"It's sliding so deep inside my pussy… the glass is stretching me… ahh… it's rubbing my insides while you teach…"
He started thrusting the test tube in and out slowly, fucking her with it while still standing behind her on the stool.
At that exact moment, there was a knock on the lab door. The old peon poked his head in.
"Principal Wang, the head office called. They want to know about tomorrow's schedule…"
Principal Wang didn't stop. He kept thrusting the test tube steadily into Lin Xia's pussy, the wet sounds barely audible under the desk.
"Yes, I'll send the schedule by email," he answered calmly, voice completely normal. "Anything else?"
Lin Xia bit her lip hard, suppressing her moans. Her body shook on the stool as the test tube kept sliding in and out of her dripping pussy. She gripped the edge of the bench, trying not to make a sound.
The peon left after a short conversation. The moment the door closed, Principal Wang thrust the test tube deeper and faster.
"Good girl… you stayed quiet like a proper student."
He finally pulled the test tube out. It was coated with her shiny pussy juices. He brought it to his mouth and licked the glass slowly, tasting her.
"Mmm… sweet. Your pussy tastes even better than your panties smelled."
Lin Xia slid off the stool, turned around, and dropped to her knees in front of him. She quickly opened his pants and pulled out his thick, girthy cock. Without a word she took it into her mouth, sucking eagerly, her soft pink lips stretching wide around the fat shaft.
Principal Wang groaned and held her long hair. "That's it… suck your principal's cock like a good chemistry student."
She bobbed her head faster, taking him deeper, her tongue swirling around the head. Within minutes he tensed up.
"I'm cumming…"
Thick ropes of hot cum exploded into her mouth. Lin Xia kept her lips sealed tight, collecting every spurt on her tongue. When he finished, she pulled back slowly, opened her mouth to show him the large creamy load, then leaned over the test tube and spat the entire cum load inside it.
"Look how much you came, Principal," she whispered dirtily. "The test tube is almost half full of your thick cum…"
She took the cum-filled test tube and poured the warm load directly onto her discarded panties. The white semen soaked into the crotch, making the fabric heavy and sticky.
Then she stepped back into the cum-soaked panties, pulling them up her long legs. The thick load pressed wetly against her pussy as she adjusted her skirt.
"I'll wear your cum inside my panties the whole day, Principal Wang," she said softly. "Every time I walk, I'll feel your load rubbing against my pussy…"
Principal Wang smiled with satisfaction, zipping up his pants. "Good girl. Tomorrow's practical will be even more educational."
Lin Xia left the laboratory with a slight waddle, the heavy, warm cum squelching inside her panties with every step. She would spend the rest of the day walking around campus carrying the principal's thick load right against her most private place.
In his dorm room far away, Ye Chen watched the entire scene through his divine sense, his own cock rock hard. The contrast between the innocent campus beauty and the filthy things she did for his pleasure only made his eternal boredom disappear faster.