You make her masturbate to you

You knew you would fuck your bitchy sister eventually, that was for certain. But you were going to have a little fun with her first.

Your pheromones flooded the room, increasing her lust and heat, while you changed back to your improved Incubus form. Your sister had always had a thing for jocks, so you took special care in building up your height and muscles, giving you an athletic figure without going overboard with the changes. You kept a bare resemblance to your old self, enough that she would recognize you.

Breathing harder now, trying to push the toy as deep as she could, she opened her eyes only to find an insanely hot demon in front of her, completely nude, stroking his 10'' dick. And there was no doubt that man, changed as he was, was his brother.

Yet she didn't care about that. On the contrary, a previously impossible thought installed in her mind.

She began to masturbate not the image of some random dude he had fucked two weeks ago, but to his brother, his new, supernaturally handsome brother. Her fingers were going faster now but the dildo was unable to bring her to climax, no matter how hard she tried. There was only one choice.

"Fuck me, bro. Please, fuck me!", she pleaded.