In the girls' room during gym class
I've always had a fascination with my nipples. I guess it started around the time I hit puberty, when I noticed that they would get firm and erect when I was turned on.
My friend Gena developed a lot earlier than the other girls in the class, and I always envied her heavy, full breasts when we changed before gym class. One week in seventh grade we were both sitting out because we had our periods. We got passes to go to the restroom, and were wasting time talking and playing with our hair.
I remember that I went into the stall to change my pad while we were talking, and when I got out, Gena had unbuttoned her shirt and was caressing her nipples through her bra. I laughed and asked her what she was doing, and she said she was trying to make her nipples hard she they'd be visible under her shirt, because she'd heard that guys liked that. I was feeling slippery and wet because I was on my period, and I remember the jolt that went through my pussy when she said that. I pretended to be fixing my bangs in the mirror, but secretly I was watching her and pushing my crotch against the sink because it felt good. The pad shifted against me and rubbed my clit.
I kind of couldn't take my eyes off her, and she asked me if I'd ever tried making my nipples stand up. I told her I hadn't, and she laughed and said I should do it with her so we'd match when we went back to class.
I said okay and unbuttoned my shirt and started to roll and tweak my nipples just like she did. I noticed that her mouth was open and she was panting, and I thought she was watching me in the mirror, too, though suddenly I was too afraid to look. I started pressing my crotch harder and harder on the sink, shifting the pad so the edge was touching my clit.
Suddenly I realized that I was about to cum, and I shook my hair in front of my face to hide it. I didn't look at Gena right away, but she was breathing hard and when I got up the courage to look, she was very obviously humping the edge of the sink. That pushed me over the edge, and I started rubbing my tits fast and furious, rolling and squeezing them while I rocked my pelvis back and forth over the pad in my panties. There was a gush of fluid into my pad and I came, both hands on my breasts.
I looked over at Gena and she was watching me, smiling. She buttoned her shirt up, came over and helped me button mine, and gave my butt a little swat as we walked back to class.
I never did anything like that with her again, but that experience gave me the courage for more adventures with girls later on.