For whatever reason stepdaughter scenes seem to be what every director wants to make. One of the problems I have with them is that they all want to cram in the idea of it being the first time you are getting seduced by your stepdaughter. This never feels convincing because they only allow 5 minutes of talking before it goes into the normal lineup of positions.
Here is my proposal, have the story be that you and your stepdaughter have been having an affair behind your wife's back for a year. This cuts out the need for the sped up story. We don't need the girl to convince us of anything. We are in on it. The back story writes itself in our minds of how we got here. Plus this can add so many other ideas.
I would start the scene in the closet with (me) facing the wall. Have the girl come from behind you telling you that mom is outside cutting the grass. Your Stepdaughter (SD) is mad at you because you have been to scared to fuck her in a week. She is tired of waiting for the prefect time. You have a little bit of time now. Your SD can drop to her knees and suck you and them tell you to hurry up and pull her pants down (or sundress up or yoga pants down) and fuck her doggy style. Have her dress like a normal hot young SD.
The scene ends because you hear your wife yelling for your SD. She has to run out but tells you mom is leaving later today so be ready.
If you can't do closet for whatever reason then do the bathroom or hallway or garage, anything that is different from the same couch we always start on The closet (a walk in closet) creates a closeness that we don't get much of if ever. Plus it adds to the realness of a true story.
The second part can be you sitting in bed when your SD comes in to tell you that your wife went to the grocery store. You have an hour before she gets back. Then go through the usual positions. But the talk can be completely different then all other SD scenes because you have been fucking every week for over a year now. Have she tell you that you haven't been giving her enough attention. Have her tell you that she wants you to leave her mom so that you can get apartment so you can do it everyday. She can say "mom has been mean to me and you aren't sticking up for me". I can think of hundreds of things she could say.
She could get a phone call from mom while she is on top of you asking what cereal she wants. She could then call back while in mish telling her she will be back in 10 minutes.
You can end it with hearing the garage door going up. Add some sound effects with the garage door and the phone calls, and with the mom yelling for her daughter.
I could add tons more detail to the story if anybody cared. I don't know how scripts are normally written.
@alexnash @kai Lep @xeddin1
