Put her dick in your butt.

Sarah continues to scrub your back with the bar of soap. Her dainty little hands caressing your back feels unusual but relaxing. Her fingers are so soft that you're not sure if it's because of the water and soap or if her skin is softer than you realized. You then feel Sarah's small hands start going more south as they go down your back towards your butt. You feel that you should stop her but it wouldn't be fair for her to have let you scrub her butt without letting her scrub yours. Sarah then starts caressing your butt cheeks, giving your ass a massage, making it extra soapy. You feel Sarah, for lack of better words, start playing with your butt as she starts spreading your ass cheeks apart then squish them together a couple of times.

"Okay Sarah, I think I've got it from here." You say trying to get Sarah off of your ass.

"Wait, wait, wait. I want to try something." With that last sentence you feel Sarah stretch your cheeks apart as you can feel her staring at your asshole. Then you feel her slippery dick head come into contact with it.

"Hey cut that out." You say defensively as you turn to look behind.

"Come on Doug, your butt is just so cute I can't help myself, I just have to put my dick in it." Sarah pleads, giving you a pair of the most innocent puppy dog eyes you've ever seen. "Please, I promise to be gentle."

"Fine." You say defeated as you turn around. Sarah, giggling with joy, connects her cock with your ass, almost feels like she is kissing your anus with her urethra as you feel her warm pre-cum spill out all over your hole. You stand there, trying to not show your nervousness as you feel the dick at your backdoor trying to get in. The first couple of pushes don't work but Sarah is determined, and after the first six big humps, you feel your asshole expand to accommodate your little sister's above average dick girth.

"I'm In!" Sarah says as her head pops into your ass. The pain hits you with a burning sting in your backdoor. You knew the first time was going to sting, but Sarah's thick dick just keeps your cheeks super far apart. You try to hold back the pain, not wanting to be humiliated by the truth that your little sister's dick is just to much for you to handle. Guys have thick girl dicks plowed into them all the time, so you just have to take it like a man. The pain couldn't prepare you for what happens next though, as Sarah starts lowering herself and you down back into the water as she sits back. She reaches the bottom of the bath as you try to sit down, but now her dick starts to cram itself more and more up your ass as you get closer and closer to the ground.

"I, I can't believe... this started with me just giving you a hand job. Now you're fucking me."

"Don't think of it as having sex big bro. Just think of it like giving me a hand job, but with your ass. You're just helping me masturbate." Your sister says, trying to reassure you, but it just makes you feel even more embarrassed. Now you've been reduced to Sarah's personal cock sleeve; and with that thought, Sarah grabs your hips and starts moving you up and down. She goes into a progressively faster pace as you are moved up and down her dong. Your anal cavity being abused by her huge penis as the waves in the bath tub get more and more rapid."OHH... I love your ass Doug. It's like it's sucking my dick like a vacuum." Sarah's grip on your hips get tighter as you can feel the veins in her dick get thicker.

"Get Ready. Get Ready, Cu- Cumming!!" You feel your ass get filled by your sister's hot white cream, as the violent spurts **** your ass off of her cock. Her young dick continues squirting out thick cream long after she pulls out of your overflowed ass. You turn around in the now white water of the bath tub, as it's hot water helps sooth your sour butt. Sarah looking like she is in another world as drool falls from the side of her mouth. Then, like waking up from a dream, she snaps out of it and realizes you're there. "Sorry Doug. Guess I got a little excited." Her cheeks turn red from embarrassment. Although she probably isn't as embarrassed as you are after being used as your little sister's cum dumpster. "Here let me make it up to you."