She's too much of a tease, bending over in her short dress, bra pushing up her tits, the way she looks at you, the way she touches your arm. You jerk off in your room with her panties, calling her name, calling your Step-sister upstairs to watch.
She's shocked, disgusted you want to jerk off in front of her, using her panties, asking her to touch your cock, it's taboo, it's wrong, it's perverse. You tell her it's no big deal, you're only Step-brother and Step-sister, but she looks at you, her dark secret about to come out, everything she has tried to keep from you for all these years, all her desires, the secret as to who she really is... all about to come out.
