Step daughters/Asexual/1st Wednesday/pleased Sandra/Masha Watches Sex/Control/Phone/Panties
"Hey, Sandy." You say, slipping in a little nick-name as you gently put your hands on her wiggling hips, causing her to stop her wiggling motions. As pleasurable as they are, they are a bit of a distraction, and you would rather not blow your load inside of your pants. Especially if you might have the chance to blow it somewhere else. "Would you like me to take that out so I can put it inside of your underwear?" You ask her.
"What!?" She responds way too loudly. "INSIDE my UNDERWEAR!?"
"Sssssh!" You shush her. "You can't do it unless you keep it a secret though. You can't even tell Masha."
"Tell me what?" Masha asks, having clearly heard you as she looks back from the couch. You just can't help but grin, you knew that would probably get her attention.
"Nothing!" You say back to her. "Me and Sandy are just playing a little game."
"What kind of game?" She asks.
"A little bit like that show I saw you watching on the TV a bit ago, I thought Sandy might enjoy something like that."
Masha doesn't say anything about that. In fact, she just stares at you and her sister from the couch, seemingly having forgotten about her show on the screen already.
"Alright," You say, turning your attention back to Sandy. "Well, you KNOW your mommy's not going to like you doing this, and she's going to find out if you tell your friends at school, so you can't tell anybody. Ok?"
"Ok!" She agrees.
You take her acknowledgement to keep this a secret as doubling for consent to what you have suggested as well, and immediately get to work.
"Alright." You say and un-snap your pants and pull the zipper down, then reach into your underwear and under where Sandy's weight is still pressing down on your dick in order to retrieve it from under her. Sandy tries to peer back over her shoulder at what you are doing, but doesn't really get a chance to get a good look before you take down the back of her pants and press your member through the groove between he panty waistband and her butt cheeks. You take Sandy and pull her back onto your dick, giving her even less to see behind herself. Of course, she realizes pretty quickly she can probably see something from the front and there's already a hand going under your front waistband when you get both hands back on her hips. Her hot, literally hot, little 4-year-old fingers rub over your pre-cum drooling glans for a quick swipe, causing her to gasp and immediately pull her hand back out.
"Alright, you can start moving like before now." You tell her.
"It's all SLIMY!" She yells at her startling discovery.
"Yeah, that will make it feel better rubbing it on your slimy privates." You tell her.
"Privates?" She asks. You miss the confusion in her tone though, and instead start helping her to gently rock her hips as you give some small thrusts forward of your own.
"Uh-huh." You tell her. "Now then, just relax. This is going to feel really good. Just keep moving your special place down there on top of my penis."
Sandra makes an uncertain sound, seeming genuinely confused as to what's going on, but she goes along with it anyway. All too quickly, you are in absolute pedo heaven as her soft cleft presses it's warmth into the top of your dick while she mechanically follows the motion of your hands and starts grinding on top of you again. You may have only just gotten it between her legs, but with everything else so far it doesn't take any more than a dozen or so strokes before you start feeling that tightness in your groin that says you are about to let a very large load go and there ain't nothing that's gonna stop it now.