This is a true story and one of my fondest memories.
I was 28 and my partner was a few years younger (this was ten years ago now). We were both straight. My partner had invited 2 of her friends from out of town to come stay for the weekend. Well not two, but a car load of people arrived, four females and one male. I knew two of the girls as my partners school mates but the other three i did not know.
They turned up on the Friday afternoon and we began drinking after a trip to the local bottle shop. I had decided to let the girls go out for the evening, it was my turn to stay home with the babies.
As the girls got tiddly, they started to get ready to go out for the night, they took about 3 hours as the ladies often do. It was summer and it started to get dark. The youngest of the ladies was a stunner. It was her 18th Birthday, I tell no lies she had turned 18 that day.
Anyway they had the car full and were waiting for the birthday girl, she stood against the wall by the door (out of view of the car load) and i wished her a good evening. Next thing i knew we were passionately kissing, i held her head and we kissed for 2 minutes long and hard. She was wearing jeans and a little top. She had gotten her belly button pierced just that day for her 18th B-Day. We engaged again for a few more minutes and then i let her go.
I was asleep and was woken at 3 in the morning to a knock knock knock at the window. The girls were home but didn't have a key. I was naked and got up and opened the door. Only two girls were home. It was my little birthday girl and her friend. My partner and her friends were not home with them.
I let them in and they followed me into the room were they proceeded to get changed into their nighties. Both were absolutely gorgeous looking. I lay in bed watching them change and patted my hand on the side of the bed gesturing them to come sit. I was worried about getting caught so we only chatted for 10 minutes before the ladies went to the lounge and went to sleep on the double fold out sofa.
An hour later, another bang bang bang at my window. the stragglers had returned home also. It was my partner and her two mates. The other male was with them (this was the brother of the 18 year old lol). Anyway a strange thing happened. My partner went and had a shower. Now this was not like her, to get home all wasted and drunk and go have a shower. Usually she would get home and be so drunk she would simple come to bed. So why the shower...?
This was strange so after she had come to bed and i had had my wicked way with her drunk ass, i decided to go investigate. I got out of bed and went to the bath room. there on the floor were her clothes and on inspection i found that her panties were soaking wet with cum, load and loads of sperm had saturated her panties, it did look like about 4 cum loads. Now this got me very very horny. She had been a naughty naughty girl and had her pussy filled with cum. No wonder she had had a shower when she got home, trying to cover up the evidence inside her pussy. Well lucky i'm an inspector gadget. LOL.
I went back into the lounge and in the dark i could hear fucking. It was my partners school mate and the 18 year olds' brother going to town on the the other couch. I heard my name faintly murmured from the double sofa and thought it was time for some pay backs. i went to the sofa and sat next to her, she was awake and listening to her brother getting his rocks off, she whispered to me, its 'MY' birthday.
I told her to come, i held her hand and led her into our bedroom. My partner was asleep. I sat on the side of the bed and pulled her close. She was wearing her panties and no bra. Her nipples were erect through her nightie and we engaged in that long deep sensual kiss we had started on earlier at the front door. She tasted fantastic. She asked.. what about "E" (my partner), i told her E had been a naughty drunk girl and we were going to have some fun. Off came her nightie, off came i panties and i found myself enjoying the softest tasty treat i had had in a long time.
We rummaged around a lot on the bed and about 30 minutes later, while we were going 69 my partner stirred. She was still rather drunk and my fingers were inside her pussy and i was playing with her clit while she was asleep. She was still very wet from the fucking she had got while she was out that night. The 18 year old was riding my face and sucking me off.
E woke up and called me a cunt. "you cunt" she exclaimed. She was dripping wet and i know she had no choice in the matter. "I know what you've been up to tonight" i told her, "i checked your panties", "now its my turn". We all sucked fucked and enjoyed ourselves for about 3 hours till the sun started to rise. The 18 year old crept out of bed at about 7 in the morning and went back to the double sofa.
In the morning the drunkards slept in, i got up early a few hours later. The 18 year old also got up early. We enjoyed an hour long shower together and were changed and up before anyone else stirred. I never even knew her name but i still think about her to this day.
They left at midday to continue their journey north. Me and my partner stood at the door as they left and waved goodbye. My partner turned to me and said "you cunt", she smiles kissed me and gave me a little slap on the face.

