All characters over the age of 18.
In case you've not read earlier chapters, note that the mother's friend is termed "aunt" as was once common practice for family friends. It would have been tedious to use inverted commas for "aunt" throughout!
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Neither of them spoke about it, but they were both conscious that the days were rapidly passing and that she would soon be leaving, to move into her new house.
As she worked and lived about sixty miles away, it was inevitable that their times together would end, either with a grande finale or simply fizzle out. The distance was the major issue. Although only sixty miles from his mother's home, he had no transport of his own, and in any case he was away at college for much of the time, a further hundred and seventy miles or so from her home town.
The other issue was the difficulty of maintaining discretion. It would arouse neighbours' suspicions if a young man turned up reasonably often to visit a woman twice his age. It wasn't viable to stay overnight, and less viable to close blinds or curtains at her home during the day. She was also due to return to work once she had moved in.
Realistically, their affair was drawing to a close.
From her perspective, it was perhaps as well. She hadn't been in a relationship for a while, and she felt it was time to try to change this. Besides, it was becoming difficult to act normal in the house and not to give his mother grounds to guess what was going on. It was difficult for Sue and her friend's son to avoid undue eye contact or other body language that might give the game away. Sue had moved away eight years ago, but Angela, his mother, was still her closest friend. Sue wouldn't want to hurt her, or to lose her friendship.
There was no denying that the limited time they had remaining together intensified their desire.. They had shared slow, lingering foreplay and after-play as well as full-on sex while his mother was at work. They had also enjoyed fleeting gropes, fumbles and flashings behind her back when she was at home.
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He awoke some time before his mother went to work. She was commencing her spell of morning shifts. He dozed off again, and half-awoke to the sound of the front door closing and the car engine starting.
A short time later he heard Aunt Sue stirring and going to the bathroom. A few minutes later she returned to her room. As usual, he was partly hard awakening. His anticipation of sex with his mother's friend made him harder still. He decided to take a shower.
He didn't bother bolting the bathroom door behind him. Having taken a pee he stepped into the shower cubicle and stepped under the shower head.
After a few adjustments to the thermostat, he was content, and began to lather himself with the shower gel. He was washing his genitals when he was conscious of the bathroom door opening.
Through the wet and steamed glass screen he saw her outline. He felt oddly embarrassed to be washing his private parts, and resumed washing his chest and armpits. He saw her plum coloured satin robe slide off her narrow shoulders and off her petite body. His member stood to attention in response.