Spank her red.

You smacked Sarah's ass with the paddle, making her jump as the paddle makes contact with her ass. Elena looked up at you, her eyes showed she was trying to beg for an orgasm. You shook your head as you continued spanking Sarah with the paddle.

You pulled Sarah back "Enough." you kissed her cheek, then put her into a tribbing position, letting Elena's legs free from the spreader bar, giving Sarah an easier time when she rubbed her pussy against Elena's.

You leaned the bar against the bed, then got on, spreading your spanks between her tits and her ass, getting both nice and red. You were slightly amazed that a vampire still had the red marks from a spanking and they hadn't gone away. "This is what you'd do if I wasn't around, is it?"

"Yes, Em." Sarah said, moaning as Elena's moans were muffled by the gag, but you know they would either match Sarah's or drown them out, given how sensitive she is. You uncuffed Sarah's hands and gave her Elena's to wrap her arms around, cuffing them so she couldn't let go until you let her.

You stopped spanking her and slapping her tits with the paddle, leaving both in the same shade of red. You kissed her cheek again, uncuffed her to let go of Elena's leg, but cuffed her again. Sarah had stopped rubbing "How should this naked body be punished further? Thoughts Elena?" you looked at the gagged sister of yours "I had to tease you." you said, making Elena glare. Elena would rather be a bitch, mouthing off, but she is reduced to glaring and scowls, something she hates just as much as being called "Slut, I want you eat out Sarah, get her to the edge, too." you helped Sarah up and laid her down where Elena was, after she moved to the end of the bed.

Sarah laid on her sore ass, making her flinch a little. Pain is still a feeling for vampires, but it is just like a single, hard slap, no matter how hard and how much you make their asses red. You lock Sarah's legs into the cuffs that are part of the spreader bar and put Elena into the same position Sarah was in. You removed the gag, letting her lick Sarah. Sarah moaned loudly as her pussy was licked, her clit sucked on, and you rubbing her clit when it wasn't being sucked on "Don't cum, Sarah. If you don't for two minutes, you can get the blindfold taken off. Want that?"

"Please! I want to see my favorite-" she stopped, but you knew she was going to say 'sister' "Our sub, naked." she tried saving herself, but it was too late.