A visitor

As Mary reaches down and gently caresses your hardening cock, the door slowly creaks open.

"Hey Mary, I thought I heard a noise from in here and... HOLY SHIT! MARY, WHAT THE HELL ARE YOU DOING?"

It was Katy, Mary's younger sister.

"Um... ah... Katy, weren't you supposed to be over at Mel's house tonight?" Says Mary, hesitantly.

"That's NEXT Wednesday." Says Katy. "Honestly John, I can't believe this... you guys have been dating one month!"s