Can't help but enjoy it

As Dawn felt the fingers slamming into her she felt her body involuntarily respond. Her hips beginning to move on their own, fucking back even as her mouth said no.

“That's it you little cunt, fuck back,” Buffy urged.

“Buffy?” Dawn asked confused. “What are you doing?”

“Showing my little sister what is going to happen to her. You are such a tease Dawn. Strutting your hot body around. It was bad enough in front of Xander, but now Willow is around too. I wouldn't blame them if they bent you over and **** your worthless ass. Or has it already happened? What kind of slut are you? You been gang banged yet?”

Dawn wanted to feel offended but the fucking her sister was giving her was preoccupying much more of her mind. “I'm not a slut!” she finally managed to protest, though the juices spilling from her pussy were telling a different story. “I haven't fucked anyone!”

“Good. That means I haven't failed you as a sister. Caught it just in time,” Buffy said as she added a third and then a fourth finger to Dawn's tight twat.

“Oh God!” Dawn screamed as her body rippled through another **** orgasm. “I said I haven't fucked anyone! Let me go!”

“I don't think you understand Dawnie,” Buffy explained as she began to seriously fuck her sister. “I am trying to be a good older sister here. As such you need to make informed choices. If you want to be a slut than so be it, I will love you however you are. You just have to realize what the consequences are. It wouldn't be right of me to stop your lesson now. You need to know the full picture.”

Buffy fingered her sister to two more orgasms before she remembered her Slaying duties. Dawn was so exhausted that she didn't even try and resist when Buffy tied her limbs off to the bed, or when she pushed a large dildo into her pussy (Buffy made sure to carry a lot of stuff in her gym bag, never know what might come up). The teenager did let out one moan of protest when her ass was stretched open by a second fake cock. The protest did not last long, both dildos were vibrators and Buffy started them off at the highest setting.

As Dawn began to let out pleasurable shrieks Buffy pulled out a ball gag. But as she looked at her sister writhe on the bed she thought there was another way to keep her quiet.

As Buffy pulled her pants down and sat herself over Dawn's face she rationalized that it wasn't any interest in lesbianism. All that talk of sex had distracted her. It wouldn't be safe to go out like this. And as it had been doing a favor for Dawn that had gotten her so hot it was only fair Dawn pay her back.