Bored Summer Evening

Well it was one summer evening and me and my little sister where riding our scooters around the neighborhood. While passing by our friends' house we saw that they where playing on their front walk. They are two girls, one about 15 and the other around 13. Let's say their names are Jacki and Mackenzie, ya that's good. Anyways my little sister decided she wanted to go play with them and I, bored to death, said, "Sure fine." So my little sister decides that she is gonna do cart wheels with Jacki ( the older one). So I'm stuck with Mackenzie. Then one of their neighbors leaves his apartment and we notice there is this little kid's blow-up bouncy thing (like a play structure or something) and it's shaped like a miniature coliseum on their front lawn. Me and Mackenzie decide to go jump on it but discover that since it is losing air it's not good to jump on. I know that she has one of those childish crushes on me. For some reason I am very horny and suggest we tickle each other. She says ok and we play a little tickle match, but then I get brave and make up some rules: She has to try to escape from the play thing while I try to tickle her and keep her in the play thing by pulling her back in. So we play this until we get tired and I suggest that she tickle me. While she is tickling me she accidentally brushes up against my crotch and I get a hard on. She doesn't notice, but by now I'm so horny I feel like jackin' off right there. So I quickly decide it's my turn to tickle her and she rolls onto her back. Though I love it and do it again this time for a full minute while tickling her until she is gasping for breath. I give her a break then go again. She tries to cover her crotch but I, acting like I am doing it to get into a better position to tickle her, throw her legs open and pretty much knee her forcefully in the crotch, and she laughs, being all tickilish, I then see an opportunity to get into her pants, tickle her stomach while slowly sliding my hand down, then stealthily sneak my hand under her waist band and into her panties, I cup her mound in my hand and tickle her pussy and then she realizes my hand and laughs uncontrollably against my soft tickling touch jerking around (the way you do when a relative playfully tickles you) and I shove my finger up her pussy and pull up then my I saw my sister returning and say bye, but first I say "did you have a fun time"? She says "ya can we play again sometime"? "Definitely," I reply happily. She never told her parents luckily and I went home and jacked off for a half an hour. Well at least I found something to do.