Erica and Mr. Ellery

It took a long time for Erica to clean all the cum out of her asshole. Her clothes were hopelessly coated in sperm, but luckily she had a change of school uniform in her gym locker. No underwear though, so she had to go without any. The cool air felt nice on her throbbing anal gape as she walked down the hallway to Room 120.

Mr. Ellery taught 12th grade physics, and Erica really wasn't sure how he might help her with her anal sex problem. But the teen was **** to be normal, like all of her friends, so she explained to him what Mr. Carstairs had told her.

The obese teacher stroked his heavy beard as he listened to her. Then he nodded slowly.

"I think I know why Carstairs sent you to me. Come on."

He led her into the huge, walk-in storage closet at the back of the classroom. Amongst the collection of scientific equipment and assorted junk was a curious contraption. It was a rectangular metal box, about two feet long and one foot wide and deep. On one of the long sides were a series of dials and buttons. From one end there dangled a power cord. Sticking out from the center of the other end was a one-foot long iron rod capped with a rounded knob.

Mr. Ellery turned to Erica, a gleam in his eye. "I call it the Rectal Rotor. Help me with this, it's heavy." The two of them lifted it together and placed it one of the tables in the classroom. The teacher took a rag, wiped off the dust, then smeared lubricant all over the metal knob sticking out from the device. He gave the pretty teen a knowing smile.

"That's the part that goes up your ass, Erica. I call it the Intruder. Oh, this will be fun. It's been a while since I played with this!"

Erica looked a little unsure. For one thing, the knob that was supposed to go into her asshole was only about two inches in diameter. After all the anal pounding she had already endured today, Erica wasn't even sure she would feel it. Then there was the matter of being penetrated by some strange machine. If a human fist and multiple cocks hadn't made her orgasm, what chance did a hunk of old metal?

But she pushed these doubts aside and jumped up on the table when Mr. Ellery told her to. She lay on her back, grabbed the back of her thighs, and pulled her knees to her chest. Her plaid skirt fell open, exposing her dilated asshole. Her head dangled off the edge of the table, and the overweight teacher smiled to himself, thinking that he might have to take advantage of her mouth while his machine serviced her rectum.

The metal knob pointed at Erica's asshole, but was about a foot away from her. The teen wondered how this thing was going to work. Her thoughts were interrupted by Mr. Ellery's cry of "Here goes!" He flipped a switch and the machine hummed to life. Erica lifted her head to look with curiosity as the teacher turned a dial and the metal rod began to rotate at high speed with a whir. He turned another dial and the brunette teen gasped as the rod extended further out of the box, the Intruder pushing forward until it just barely touched her asshole, then drew back to its original place. Back and forth it went, the speed getting faster as the teacher played with buttons and dials, the rounded end teasing Erica's anus.

He grinned at her. "Here's the best part." He twisted another dial. This time, as the rod rotated and moved forward, the Intruder expanded in width, doubling in size to the size of an orange. Another twist of the dial and the knob that was to enter her ass was the size of a grapefruit. And then a bowling ball.

"Oh, my god," Erica said, her eyes widening in alarm.

"Isn't she a beauty?" said Mr. Ellery excitedly as he dialed the Intruder back to its original size. "I can control the rotational speed, the velocity of the penetration, the distance plunged into your ass, the volume of the insertion -- oh, so many variables to play with! Just rub your clitoris like a good girl and we should be able to figure out just what configuration can give you your anal orgasm!"

Before she could register her considerable doubts about the safety of this strange device, the teacher laughed wildly and with a flick of his wrist sent the metal knob plunging into Erica's asshole. Slightly bigger than a golf ball, the spinning Intruder pushed 6 inches inside her before retracting all the way back, then repeating the motion endlessly. Despite her skepticism that she would even feel such a small intrusion after her previous anal pounding, Erica cried out. She could definitely feel it, the metal ball rotating rapidly within her, shoving up inside of her. As instructed, she quickly began to finger her clitoris fiercely, so **** to cum.

As the teacher adjusted dials and buttons, the Intruder moved into her asshole faster and faster, and deeper and deeper. Erica screamed when it grew to the size of a grapefruit, her tender teen rectum completely filled, her anal ring obscenely stretching as it was penetrated over and over by the massive insertion.

"Rub your clit!" barked Mr. Ellery, determined that the student should orgasm on his beloved machine, and Erica dutifully obeyed. Her whole body felt like it was on fire, her asshole ached, but she couldn't deny the way her clit hummed and throbbed, matching the oscillations of the Rectal Rotor.