Of course!

"Of course I will!" Sarah says, and kisses you again. "I love you, Katherine. I know I'm your sister, and I shouldn't feel this way, but I can't help it."

You sigh breathlessly as she kisses you over and over again. You open your mouth and allow her hot, moist tongue to mingle with yours. This is hotter than any kiss anyone has ever given you. You bite each others' lips to the point of drawing blood. Like crazed vampires you take turns sucking the blood from each others' lips. The salty and slightly iron flavor of her blood drives you wild with desire.

Sarah pulls your top out of your skirt, and runs her hand up underneath to find the front catch of your bra. She deftly finds it, and springs open the cups confining your breasts. She softly caresses them, and runs her fingers over your erect, perky nipples. "I want to suck your nipples" she softly coos into your ear. You lift up your arms, and allow her to remove your top, and slide your bra straps down your arms. Then she pushes you down on your back on the sofa, straddling you as she bends over to kiss your naked breasts.

Just as Sarah is about to take a nipple into her mouth, the door opens. "What the hell are you two doing?" a familiar voice demands.