I'd been living with my girlfriend Ann for a couple of years. We had a nice 2 bed flat in a converted Victorian house in a trendy part of town near to the local university. Ann had a sister, 2 years younger aged 22 called Emma. Emma had been living with her parents but had just got a place at our university. Rather than rent a place or move into halls of residence Ann suggested that Emma could stay with us in our spare room for the first year of her studies.
I was fairly relaxed about the idea as I got on well with Emma and she was very easy on the eye. Despite being sisters they were nothing alike physically. Ann was brunette about 5-7 tall and a size 12, whereas Emma was a petite blond 5-2 tall and just a size 10.
Anyway, Emma moved in and things continued generally as normal other than there was sometimes a queue for the one bathroom and there were more discarded clothes strewn around the flat. Untidiness was something both sisters did share in common. It seemed almost every day I found discarded items laying around including some very skimpy erotic lingerie which Emma seemed to like wearing.
I did wonder if having Emma in the spare room next to our bedroom would curtail some of Ann's bedroom behaviour. The wall between the two rooms stopped short of the ceiling to allow some borrowed light from our room which was naturally lit, into the second room, which didn't have its own window. Whilst this allowed a good amount of light, it also meant you could hear everything in each room.
Ann was very vocal when we had sex, beyond the average gasps and groans, often demanding that I 'fuck her harder', or 'shoot my cum deep inside her'. I very much enjoyed talking dirty during sex, but now that Emma could hear everything I thought Ann might be more subdued. But it seemed the opposite was true and Ann seemed to be even louder when she knew Emma was in her room.
Ann was also quite submissive and I would often spank her, especially when fucking her from behind. I loved to land a flurry of hard spanks to her bum just before I came. Ann would always encourage me to spank her harder and make her ass red.
So we continued fucking as normal, even though Emma could hear our every move, especially when I spanked Ann. I'm sure Emma was getting turned on listening in to us as I could often hear little gasps and the rustle of bed clothes after Ann and I had stopped fucking. Nothing was ever said between us, even though we both knew we were listening to each other.
I knew Emma had a new boyfriend called Gary and we'd been out together as a foursome a couple of times. I thought he has a bit old for her and a bit stuck up, but she seemed to like him and began spending more time at his place, certainly at the weekends.
Then one-day Emma asked if Gary could stay over for the weekend because the heating had broken in his house and it was freezing. Ann and I were going away to a wedding and would be staying for the weekend so I said yes and told her to enjoy herself!
We left early on the Saturday so we missed Gary arriving. The wedding and reception was great and on the Sunday Ann accepted the offer from an old school mate, who was also at the wedding to stay on and go shopping with her. The school mate had offered to drop Ann home after shopping, so it meant I could miss the shopping and get home first.
I got home about 3pm, there was no sign of Gary or Emma, but I shouted hello anyway in case they were both in her room. I then began to unpack, lost in my own world until I heard a quiet moan and a little gasp. This was then followed up by the unmistakable sounds of a bed creaking quietly. That was why there was no sign of them, they were in bed fucking. I stopped unpacking and listened to them fucking which got louder and louder as they both neared climax. Gary clearly seemed to know what he was doing as he kept Emma gasping for about half an hour before he finally came. After that I heard him saying he was off to his flat to check on the heating, then the front door opened and slammed shut as he left.
Shortly after that I heard a scream and Emma came running from her room shouting there was a spider in the room and she wanted me to get rid of it! I wandered into her room and scooped up the spider and threw it out of the front window while Emma stood in the kitchen with her back against the wall. It was clear she didn't like spiders!
I told her it was all clear but Emma insisted I come into her room and check it was all clear with her. I was willing to oblige if it made her happy. I did a quick sweep of the room and there were no more spiders. There was however clear evidence of their recent fucking with the unmade state of the bed and what looked to be a cane half covered by the duvet. I had missed that when I first removed the spider, but now I pulled it out from the covers and asked Emma what she used it for?
Emma blushed and stumblingly said it was something that Gary had brought and I could guess was he did with it, especially with the way I spanked Ann. So, she had definitely heard me spanking Ann during sex. I smiled at her and said I had a good idea, but maybe she should tell me. Emma gave me a crooked grin and said rather than tell me, she would show me. With that she turned around and slipped down her jeans and bent over the edge of the bed. I could now she her bum was clearly marked with six violet welts from the cane. Emma turned her head and said Gary had caned her on Saturday night, he'd given her three with her knickers on and then three on the bare, after which they'd fucked.
I asked her to tell me more and Emma said that the first three stokes were hard, but the next three with no knickers had been real stingers. I was surprised that the three strokes on the bare were worse given that Emma always wore such skimpy knickers that would afford such scant protection. Emma said she thought it was more about fact she was bent over, with her knickers around her knees that made Gary cane harder - a point I could fully appreciate. She said Gary caned her often and always hard, which Emma admitted she struggled to manage sometimes, especially when he gave her 12 or even 18 strokes.