Having read though some of the stories, I don't feel alone and decided to share my own true story.
All this happened when I was 14 and sis was 16.
As we were both bored one night with nothing on T.V. we decided to play a game, it started with the usual noughts and crosses, followed by hangman (guess the word/film etc) sure you know them both. This then progressed on to the classic connect four game. As parents were out for the night and never returned till late, had a lot of time on our hands.
After a while of playing the game it was all becoming boring just winning and losing, when sis said, how about dares, loser does it, in agreement with the stakes at hand it began. Firstly just silly dares like go make a drink, or fetch some food to eat for the winner.
By a few more games the stakes on dares were getting higher, mom had an exercise bike in the living room and after losing a game, was dared to ride the bike at high speed for two minutes or forfeit a punishment in not achieving the goal. Right, your on I said.
Pointing out a high km rate to reach, I began to push the speedo needle upwards peddling faster, maintaining the speed rate became harder as the two minutes went by. Suddenly my foot slipped as I was only wearing socks, and the needle dropped below.... Ohhhh you failed, sis said, trying to protest the outcome to no avail. Physical punishment she gleed but... I donno she said if you will do it? Up to you but you could always win a game yourself and dare. Your on I said, go ahead.
Pull your trousers and pants down and run to the front window then to the back one. I looked at her and said 'Now!' of course now!
I pulled them downwards to my knees, shyly turning my side to sis and ran up and down the room, sis laughing as I did.
Quick as I could I pulled them back up and returned to the game, thought my cock was getting harder, it was quite sexually enlightening having done that and surprised me so. I lost again and sis said same dare laughing, not fair unless I wear my trainers, I said.
Right then I got an idea, if I win again it is a double dare you do, or if you win I do your dare! ok? sis asked, Your on.
Winning that game, I eagerly said, 20 star jumps no top on. Ok sis said, jumped up with out bothering at all, pulled her t-shirt off leaving her white bra on, breasts exposed at the top a low cut bra. No, no top I said,
Didn't say about my bra did you, and continued doing the 20 star-jumps.
Though it didn't really matter because I still got the same satisfaction of seeing her breasts bouncing. My cock hardening even more watching her, this was so risky and exciting so much to me.
Next game sis won...... double dare or not? Double knowing that I would get out of this dare and a chance for me to win.. Damm I lost the next.. Sis jumped up and said.. you better do it. Off she went out the door and heard her going up stairs. Before long she returned with some clothes in hand..... dare is put these on.. handing me her school gym kit.. the tight full gym knickers and high neck top, short cut shoulder tight fitting t-shirt. we girls have to wear it at gym, so think it suit you. It wasn't the gym kit that bothered me.. it was the hard-on in my pants that would show. Come on, come on, a dare is a dare, you chickening out?
I took the gym kit and went to the hallway to change.... No in here in case you run chicken. I stripped off turning my back... there was no-way I could hide my erection in the gym knickers, everything was soooo tight. I luv the girls at school in there's, especially the older girls with their firm smooth bodies and tight asses.
I dressed, then turned to sit quickly.... Oh no boyo, its a double dare..... Oh my god she laughed, you've got a hardon, dirty little bugger she giggled. You like them I bet.. she taunted me.
On the bike and two minutes again, no failing. I got on the bike as she stood in front, ok GO, I almost made the two minute mark.. but failed.. Sis just said... Show me it looking at the gym knicks. I got off and just pulled the gym knickers down..... oh fuck that's so fucking hard, my erection was pointing straight upwards tight against my stomach, damm it was so pulsing at full hardness, I'd got it really really solid before, teasing and pulling, almost cumming then stopping, this was different... I was looking down at it, the head bigger than ever, my erection twiching bobbing like mad. I went to put my clothes on, when sis shouted Oh no.. you lost you keep them on.. sit and play.
I couldn't concentrate on the game and ended up losing to another double dare. Back on the bike and this time gym knickers down but so you can peddle.. what speed I asked, none but no holding the handles hold your cock and tug it as your double dare.
I began my double dare and was so horny just wanting to shoot my load, I was trying to co-ordinate the peddling, wanking my erection and stay focus, but that had gone completely. It wasn't long before my cum was shooting upwards, outwards and splattering everywhere, my legs shook and went weak kneed I'd never cum that high, that far and that amount before, I was totally exhausted and stopped peddling the exercise bike.
Sis slapped my butt..... carry on there was no time limit set.. I began peddling again, no arguments there from me.. anything to please her, I was under her commands and dares now.
This led to more games and dares and if anyone enjoyed this I'll post more.