Your Step-Daughter has a problem. Unable to stop masturbating for days on end, and mortified that you've been able to hear her touching herself, she has no choice but to turn to you for advice. You assure her there's nothing wrong with her and that her insatiable arousal is simply her body's way of trying to send her a message. Pretty, fertile girls like her need to be impregnated, and the only way for her to sate her desire is to be bred. She's relieved to have found a simple solution to her problem, but she doesn't have anyone who can help get her pregnant. Since you're such a generous, loving step-daddy, you offer yourself as a sperm donor. She's touched and delighted that you love her enough to impregnate her, and happily accepts your offer without hesitation.
*CREAMPIE ALERT*
Originally a custom video, but no names are used.