A few months ago my friend and her sister came to stay at my house, we were going to a party the next day so they had to spend the night. We spent the day watching dumb movies.

Later in the day my friends sister came over to me and asked me if I like liked my friend. I reluctantly said yes. I trusted her not to say anything.

My friend was on the couch and my friends sister was in the spare room. My friend insisted my sister had her own bed.
That night I was asleep and my friends sister woke me up. She was in her underwear. I asked her what she wanted and she said she had a suprise in the living room.

I reluctantly agreed to follow her still in my boxers into the living room. She pointed to the couch. To my suprise my friend was lying naked on the bed.

Her sister urged me to go and "get a closer look" I decided it wasn't the best idea and refused but she pushed me towards the couch. I didn't want to get into trouble but I knew that she was hard to wake up.

So without really thinking it through I began fingering her. Her sister giggled and urged me to continue. And I did. I'm not sure how long I was there but after a while I thought that i should stop before she woke up.

The sister asked for me to do it to her as well. And now we are dating.

It turns out my friend had asked her sister to convince me to do it as a joke. She just laughed when her sister told her. I don't know whether she believes it or not.