Nope... it's Gwen

On the other side of the door is your sister, Gwen.

For a long time, you just stare at each other. Your brain is just spinning it's wheels in the three-foot-deep-shit you just suddenly landed in. You know her well enough that you can tell she's in a similar condition. She blushes, and you're pretty sure you blush back. Your jaw opens and closes a few times before you're able to speak. "Hi..." you start, but then you immediately have to stop yourself because you almost called her by name. To her, you're just some strange girl, you remind yourself. Some strange girl who clearly had sex last night at her brother's girlfriend's apartment.

"Um... is John here? John Doe?" She asks softly, craning her neck slightly to try to see past you into the apartment. You don't have anything in particular to hide, but you find yourself instinctively pulling the door mostly closed behind you as you answer "no."

"Oh... Well, then, do you know where he is?" You wrack your overtaxed brain for an answer. It remains unresponsive. Eventually, you just go with the same answer you gave a second ago: "no."

Gwen apparently doesn't have any further questions planned, so you're back to awkward silence. You lift a hand to your face to brush away some stray hair. As you do, Gwen tilts her head downward and her blush deepens by several shades. You freeze. Slowly, the realization dawns on you that you aren't wearing any pants. Or underwear. And that lifting your arm has also lifted the one garment you are wearing, which was barely covering your pussy to begin with.

You leap back into the apartment, slamming the door in your sister's face, and run all the way back to the bedroom. You close the bedroom door behind you as well before simply curling up into a ball on the floor, slowly dying from shame and embarrassment.