"Katy, you can stop masturbating now," said Clara. Katy stopped fingering herself and sat up, a relieved expression on her face. She was panting and sweating, her face almost as red as her pussy. Her fingers were slick with juice.
"You should really be more careful what you say," Katy admonished. "I can't stop myself from doing what you tell me to, remember?"
"I know." Clara grinned. "So did you have a good time?"
Katy was still panting, out of breath. "I felt so horny, hornier than I've ever been in my entire life. I just had to keep fucking myself. I lost track of time, I didn't care about anything except making myself cum. Where were you, anyway?"
"I fell asleep."
Katy glared at her.
"I didn't mean to! I was tired, it just sort of happened, I'm sorry. Well..." Clara looked at Katy. "Maybe not that sorry... It's hard to feel bad for someone who obviously had so much fun. How many times did you cum, do you think?"
"I don't really remember. I think around twenty."
"That's a new record for you, isn't it?"
"Of course it is."
Clara thought a little, considering what to do next. "Katy, go lie down on your bed." Katy obeyed, flopping herself down lying on her back, making herself comfortable with the pillows. "Now Katy, start masturbating again. And don't stop until I say so. We're going to set an even bigger record for you." Katy's hand shot down to her crotch as she spread her legs apart. She started rubbing her clit with her thumb, sticking two fingers into her pussy and sliding them in and out. Her cunt made little wet noises, and her breath started coming in little gasps. Clara felt a little more wetness between her legs, and eagerly stripped off her clothes. Naked, she lay down on the bed next to Katy and started slowly circling around her cunt with one finger, her other hand clutching her breast. She could hear Katy's moaning right next to her ear, it sounded like she was reaching a peak, making little, high-pitched "oh" noises. Clara slid a finger in and moved it around, then another, feeling her hot wetness. She started to fuck herself to, trying to move her hand in time to Katy's. But Katy already had a head start, and reached orgasm before Clara did, her body shaking slightly as she let out a deep, satisfied moan and then started fucking herself again. Clara's orgasm came soon after, and it felt great. She was so turned on right now. She worked herself to a second one, trying to time it better with Katy's, and the two came almost in unison.
Clara, unlike Katy, was tired, so she curled up with Katy, resting her head on her chest. It was relaxing to her her roommates faint moans echoing within her body, to feel the little spasms run through her muscles. She soon fell asleep again.
When she woke up, it was dark outside. Clara checked the clock - nearly an hour later, and Katy was still going at it, as strong as ever. Clara stood up and got dressed. "Katy, I'm going to get dinner. Do you want anything?" She grinned wickedly. Katy said nothing other than "oh..." Suddenly, an idea popped into Clara's head. "Katy, I'm going to try changing your body so that you don't have to eat, or go to the bathroom, all you need to do is masturbate." She thought about it in her head, focusing on the collar, like the shopkeeper told her to. "Did it work?" she asked. Katy nodded her head. Clara, dressed again, went down to the dining hall, leaving the door unlocked behind her and Katy well on her way to another orgasm.