First of all I'd like to ask, who knows those stories about a boy getting it on with a mature woman? Either he gets seduced by her, or she is something like a tutor in sexual matters. In most cases, she is the one who gives the orders, and for this idea, I'd like to keep it that way. What would you say if you could play through this situation you have only heard of from others?

Setting the ground
So, my idea is that you are a junior or senior in high school on summer vacation. The story starts with you arriving at summer camp (makes mini games possible and every-day-duties), or you stay at home and do a side job, at a drive in or deliver newspapers in the morning, or maybe even working in the mall.
If you are at summer camp, you notice that there is a MILF living in a house nearby, a house at the lake, or a house boat. If you stay at home, you notice a MILF moving into the neighbouring house. Either way, from now on the story starts to play out as a light version of Hitchcock's "Rear Window". I don't mean the player to observe a murder, I want to play the voyeur. This means, you start to (seemingly secretive) observe her through the windows of her house, doing the gardening, swimming in the pool or the lake. Seems as if she was a nudist or exhibitionist, because after a while she gradually starts to do those things topless and even in the nude.

Getting to know your neighbor
Finally, you meet her. There are some possibilities I currently think of: Sports field or beach (when at summer camp), side job or mall (when at home). She starts talking to you ("Hey, aren't you the boy from next door?/I know you from summer camp!"), you do some smalltalk and move from family (she is divorced and her little son spends the holidays with his father and feels somewhat lonely) to sex and erotic. Turns out that she put on a show for you and enjoys to turn your head, and with the right words, she decides to take you with her, for example: "Not every boy appreciates a real woman..."

Trying is better than studying
When at her place, I'd say that you have to follow her orders, otherwise she instantly throws you out and never talks to you again. She orders you to strip her, then you go to the living room and she tells you how to arouse her with mouth and hands. You're pretty surprised that she lactates although her son is something around 4 or 5 years old, and she tells you that she keeps pumping herself for the fun and feeling of it.
After a while she decides to play with you as well (hand- and blowjob), and after you come in her mouth, you finally go to her bedroom. (She says, "You'll be up again in no time, I'm pretty sure!", and wiggles her naked juicy ass, making your whole body tingle.) She still continues to give you orders, but as she comes closer to orgasm, she starts to loosen her "grip" until she is a slave to her carnal desires. ("Don't you dare to come so soon!") The young stallion that you are, and the reason why she took you home with her, you don't stop on her orgasm and continue to pound her, making her scream and squirt pussy juice on every orgasm and her breasts leak runlets of milk, until she passes out on her fourth or fifth orgasm.
You could leave, but I would recommend you to stay. You could gently caress her body (resulting in soft moans), play with her breasts, drink her milk, and when she comes to her senses again, she's very happy you stayed with her and tells you she'd love to do it again, anytime. (Maybe also anywhere.)
If you have left, I would say that you could still have sex with her, but it would be quite deadhearted and mechanical, since she got the impression that you don't care about her and only want sex.

EDIT: Age difference
Maybe as an idea to keep the impression that you are (many years) younger than her, she is taller than the player?

A/N: I'd like to apologize. I don't mean to spam this forum. I have posted the idea that I told you in this topic as an answer in the thread started by MasterN (Title: Story Suggestion ) because I thought it would make sense to have the ideas dealing with the same theme in one thread. I made up my mind and find it the far more better idea that every story suggestion has its own topic. Therefore, this message board seems to be more of a story archive, and mixing up different story proposals in one topic only results in a turmoil that nobody understands. I am really sorry.

In order to keep the convention of having two girls to play with in XSP-stories, I thought about how to continue this story.

First of all, I personally started to favour the situation that the MILF is your neighbour (I will call her Victoria from now on), or rather the neighbour of your parents (which are never on-screen and shout at you, similar to Howard Wolowitz's mother from The Big Bang Theory ), so when the description of the ongoing story seems to be limited to a neighbouring house, with some thought it surely can be modified to fit the summer camp idea if that location is preferred.

Your desired partner is currently unavailable
Now to the continuation. The idea is that (either in real time or with fast forward) a week passes on, and as you want to visit your friendly neighbour, nobody opens the door. You continue your day, and when you come home from your side job, you notice there is someone else in the neighbouring house instead of your beloved MILF. You might observe her as well, but she is not as revealing as Victoria was, meaning that she is never naked outside and will hide and maybe even confront you if she catches you ogling her. You either go over and talk to her, or she starts talking to you when you mow the lawn. Turns out that she is Victoria's niece Nicole, and she is supposed to look after the house as long as her aunt is away, could be holiday or job reasons. Job might make more sense, since Victoria went without a word and left her niece to tell you.

So, how are you supposed to get it on with Nicole?
I would like to mirror the student-teacher-situation that you experienced with your MILF before, which means that you're going to be Nicole's teacher. It could be possible that Victoria talked about you and made Nicole curious about what made her aunt this cheerful recently, but I would prefer the idea that Victoria didn't tell her niece about your relationship, so you have to get to know Nicole first before you can approach her. I'd like Nicole to be quiet and shy at first, in order to contrast her aunt (and maybe Victoria had something on her mind when she sent Nicole to look after her house).
You help Nicole around the house, go out a few times and finally talk about Victoria and your relationship. Nicole is surprised, but also disappointed that you have slept with her aunt, and your date ends rather abruptly. You go home and it seems as if everything is said and done.

A sudden twist
The next day, she unexpectedly visits you at your work. She says that her aunt only slept with you, nothing is decided, and if Nicole would cut it off, it would surely be a mistake, because you regret those things you have not done. Either you and Nicole stay together, or you just spend a nice night or week with each other, but in the end she won't question herself if it was wrong to let you go, and she tells you to come to her house this night. You visit her in the evening and start to undress, but she tells you that she never was with a boy before, so you are supposed to be gentle and go slowly. Possibly you only undress and masturbate her in the first night, the next time she's comfortable being naked around you and wants to taste you, and when you come together for the third time you'll finally make out. You can watch her being naked in the house, and on her last day in her aunt's house, she's willing to try anal with you.

EDIT: Keep the MILF
Could be possible to keep the MILF-Theme and make Nicole a friend of Victoria.

2nd EDIT: More branching
Thought about you talking with Nicole about her aunt. There could be a decision for the player to make, namely tell the truth or lie about what is going on with Victoria. My suggestion would be that if you lie to her, the date goes on as normal and you can make out. The other way is that you tell her the truth, the date ends, but she appreciates your honesty and still wants to meet you.
(Possibly the thought bubbles could give hints, for example, "I guess I messed things up big time", but when they appear, they signal that everything goes as it is supposed to be and you don't have to load your last save.)
On first sight, there seems to be no difference, but I imagine the following: When you lied to her, you get it on really quick with Nicole, but when Victoria returns, Nicole learns the truth and she cuts off every contact to you. But when you told her the truth, you come together at a slower pace, and when Victoria returns, Nicole tells you where she lives, and you can meet both afterwards.