Hot Summer Job/Tell your sis you want to check how deep it is
You let go of the plug and your sister's ass sucks it right back up against her butthole. Leaning over so far that your head is nearly inverted, you peer straight into Bree's pried open slit as the bulge inside her pussy retreats slightly.
"I wanna check how deep this thing goes."
"Huh? What do you meeeeEEEE!"
With one quick push you slip your middle finger into your sibling's gaping little hole, reaching into her pussy to feel the contour of her plug from inside her. It's a bold move but you feel especially confident about it after your long night with Carrie, although your sister's pussy is way more tight and super supple and she clamps down on your finger as you push inside her.
"Riiileeee!" Bree whines.
"Just wait a second."
Bree grumbles and puts her head down. You know you're crossing boundaries and you don't really care. If she was willing to let you pry a buttplug out of her ass then she couldn't be that far off from getting fingered. Or maybe she just trusts you more than she should. Either way, you don't mind lying to yourself now that you're here.
You wiggle your digit inside Bree's young slit and rub the bulge that is pushing against her vagina. Bree squirms and complains as you twitch your finger, rising onto the tips of her toes, but that's all. She otherwise lets you explore her, at least a little. Your finger curves around the broad bump displacing her tight tunnel and as you wiggle past it you see the jewel outside shift down as the plug is pushed up.
"This is pretty big, isn't it?"
"Y-yeah. Just... hrnng... take it out!"
Ignoring her for another moment, your finger twists from side to side to help spread her wetness and coat your finger. You then pull back a few times, giving her tiny thrusts that you could still pass off as nothing but that make her huff and groan, before furthering your assessment of the situation.
"Yep. It's not small."
"Riley... mmmph... quit..."
"Okay, okay."
Letting go of Bree's ass cheek, you keep your finger well inside her while your other hand latches onto her jewel again. With steadily increasing pressure you pull back and watch her asshole pucker outward once more, then watch the center of her butt bulge more and more as the plug presses against the inner rim of her anus. You also feel the bulge travel along the length of your finger, the plug pressing her vaginal wall against your intrusive digit. Bree is still a virgin (you have to assume) but she already knows what being double penetrated feels like.
Your sister groans again as you draw out the extraction of her plug. She seems frustrated, maybe even annoyed, but there's no way she dislikes this. With how hard you can feel it press into your finger through her pussy you can imagine why she doesn't mind. Your friends have argued about whether any girls actually like anal, but opinions were varied. You can't speak for other girls, but your sis sure seems to like her plug, which helps explain why she's had no problem keeping it in all day.
Bree's bum lifts a little higher as the plug teeters on the edge of release. You start to see the underside of the flared metal peek through as her asshole opens up to make way for it. With one more small tug you finally pop it free.
"Mmmuhh!"
Your sis yelps and shudders a little, a visible shiver going through her while you watch her gaping asshole close up tight. You wait for it to close all the way before you slide your finger out of her. Unless you don't...