Bottomless at a friend's house.

When I was living at my parent's house I used to have a friend named Jennie. We met in high school and we would hang out together a lot. She had a sister named Anne and she was quite shy around me. I remember when I first met Anne when I first went over to Jennie's house to have a sleepover, the three of us were in our jammies sitting in Anne's room discussing some "adult" subjects when the topic turned towards butts, specifically our butts. I said that I thought my butt was too small and Anne wanted me to show her to verify. I stood up and pulled my pants down about 3/4 of the way just to show her since I didn't have underwear on and I did want to know if I was just being insecure or not but I was a bit uncomfortable showing someone I didn't know very well my bare bum. Anne assured me that my butt was fine but from then on she seemed a bit off. I just assumed despite her being the one who requested it I did make her a bit uncomfortable after all.