No, she doesn't accept

"Wait!" Gretchen yelled. Professor Klein stopped quickly, leaving only the first diagonal line of an "A" on her paper. She looked up at Gretchen inquisitively. "Don't give me and A+. Don't give me a grade." Gretchen pleaded.

"Don't you want a passing grade?" The professor asked. "What you did here deserves it. I understand that it was big for you. Maybe not for someone else, but we're all different hon."

Her professor's reasonableness just made it worse for Gretchen. And she was right, this small 4-person orgy wouldn't be that big of a deal for anyone else. "I don't." Gretchen said emphatically, the cold basement air covering her naked body with goosebumps. "I don't deserve it. Not for this. And also...."

Professor Klein smiled as if she knew there would be an 'and also...' The slaves smiled too.

"And also," Gretchen went on. "If you pass me, I won't have a reason to come back." There it was. Professor Klein knew it was coming and Gretchen knew it was true. "I'll go home and convince myself this never happened and I'll become a cold bitch again eventually, I know it. Please, make me have to come back."

So Professor Klein obliged and told Gretchen that she wouldn't receive her grade until after a few more sessions. And that made Gretchen happy.

"I'll come back tomorrow." Gretchen said eagerly as she pulled her jeans up and slipper back into her blouse, feeling overdressed just from being dressed.

"Come back the next day. I have office hours tomorrow." Professor Klein shot back. "Sorry, there have to be other things in life but sex."

Something about hearing that phrase from her professor made Gretchen extraordinarily sad.

Two days later Gretchen was in Professor Klein's basement again, against the wall, stripped completely nude her arms pulled high above her head, tied at the wrists and fastened to some hook off the ceiling.

Her skin tightened and her body shivered as one of the **** men wrote something across her smallish breasts in marker.

"What does it say?" Gretchen demanded so Professor Klein held up a mirror. The words said "Bad Girl" Gretchen nearly collapsed from desire.

Then all three slaves took turns eating Gretchen out all night. It went on for hours as Gretchen's loud moans turned to exhausted whimpers.

She came three times and was a mess of jelly, just held up by the ropes binding her arms. "There's more" She heard Professor Klein's voice whisper into her ear as her eyes were closed.

Then she felt a hard metal thwack across her breasts. It hurt immensely. Her eyes shot open.

The **** girl had a thick metal ruler and smacked her again and then again. Gretchen's body went crazy. The pain was intense. "Wait!" she shouted. "Wait! Stop!" She wasn't sure if she liked this or not, but needed a brief respite from the pain.

Then something unexpected happened.

Professor Klein knelt down before Gretchen and buried her face in the girl's sopping wet pussy. The feeling was sensational. The professor was better at eating her out than any of the slaves. She fidgeted, unable to do anything about the pleasure.

Then another hit from the ruler across her breasts. The pleasure from her groin seemed to travel up through her torso into the pain of her breasts and explode in a feeling of pure ecstasy.

"Hit me again!" Gretchen shouted.

After that Gretchen couldn't wear a bra because of the pain as it squeezed against her sore chest. And it was three days before her next appointment with the professor. She could think of nothing else.

And Gretchen found herself bound again just like the last time, wondering if this was going to be the way it went for a while. She'd be fine with that.

"Please, hurt me again." she begged. "Please, eat me out and hurt me again, just like last time." Her breasts were still covered in red from the previous punishment. "You can smack my butt too." She insisted "Do it, smack me and make me cum."

Just then Professor Klein walked up to the girl and did smack her, hard across the face. Gretchen's head flung to the right, her hair falling into her face, a mess. "They're my slaves, not yours." The professor said as she gave Gretchen a peck on the lips. "You're starting to talk too much."

So a five-inch dildo was procured and pushed into Gretchen's mouth by the girl ****, as one of the man slaves wrapped tape around her head to keep it in place and the other man **** wrote something on her chest again. "Silent Slut" it said this time. And the realization of what was happening and the feeling of the dildo poking the back of her throat almost made Gretchen cum alone. She felt like she could cum so easily now.

And she did cum that night, five times, and as Professor Klein at her out, the final one to do so again, the **** girl pierced both of her hard pink nipples with a needle.

Two days after that Gretchen showed up for yet another session.

"Don't you have any demands for us this time?" Professor Klein asked, already knowing the answer.

"Do whatever you want with me." Gretchen whispered.

That night was different. "Tonight you go down on us." Professor Klein insisted. And once Gretchen was stripped nude and her ass filled with a thick plug, again held in by tape wrapped around her, she began, first lapping at the clit of the **** girl for what seemed like an hour until her chin was covered in juice, and finally the girl came. Then both men bobbing on their big cocks, coughing as they poked the back of her throat, drool sliding out of the corners of her mouth. In no time, they came too. She swallowed it down.

Which left Professor Klein. Gretchen beheld her amazing bald vagina and then pushed her face into her teacher's wet crotch. Professor Klein came quickly but demanded more. So Gretchen kept going. And again. And again. Until Gretchen felt like she might drown or suffocate. Hours passed and the professor came numerous times.

And finally Gretchen relented, the taste of men's cum and women's cum filling every inch of her mouth, the sensation of her tight ass filled all night long. She thought about the girl she was just a short time ago. The cold prude who hated sex. And what was she now? The professor's happiest whore. She could live with that.

Which is why she was surprised when Professor Klein said "This was your last session," as she finally pulled a pair of panties onto herself at daybreak.

"No! It can't be!" Gretchen begged "Please, I need more to earn my grade."

"You've earned your grade." The professor insisted as she wrapped her arms around the shocked girl. "And you've done a great job. You've been a quick study. But this always had to be temporary."

"Please!" tears were streaming down Gretchen's face now, mixing with the cum on her chin. "You can't just stop! I don't want to stop! You've changed my whole life!"

The slaves looked at each other dubiously. Professor Klein grimaced.

"I'm yours! I'm all yours! I'll do or be anything!" Gretchen was more **** than she'd ever remembered herself being