With adjustment

You fumble with your pants as you hang on to your tiny sister, hastily pulling out your package. You stroke your fast-erecting cock and lower her to be level with it. She turns to see what the adjacent commotion is and freaks out, writhing and squeaking something unintelligible.

Soon, your cock is erect, but your face falls as you can clearly see it’s only about a third of her height. No matter, you think, dropping your dick in favor of the app.

A quick swipe, and your dick balloons to a full 8 inches! You stagger slightly as the blood rushes into your newfound length, and your sister shrieks in horror as even your penis dwarfs her.

You almost jerk to finish right then and there, but your sister’s complaint draws your attention back to her. You can see you’re too big for her now, but that shouldn’t be a problem for the app.

Another quick adjustment, and her insides are as flexible as a fleshlight. You move her carefully so that her cunt is right in front of your massive dick, and thrust deep within her.

Her shouting is cut off as your cock floods her insides, knocking the air from her as her entire body stretches to accept your cock. The fabric of her crop-top and skirt rip away to reveal her tiny tits wobbling on the surface of your pulsating dick and you see her frail legs spasm and kick involuntarily. Her neck bulges and her mouth puckers as her cheeks bloat with precum that she practically drools.