Every day, I secretly play with the nipples of my super introverted stepsister while hiding from our parents. At first, she didn't like it, but recently she's become super sensitive and prone to quick orgasms, making lewd faces as she cums over and over! Now she's basically my personal sex toy! The desire that can't be satisfied by just playing with her nipples eventually escalates to penetration. My stepsister drools and gushes with arousal from the nipple play, cumming even from light penetration! And if I really start thrusting, she goes crazy with multiple intense orgasms! This is the result of training her entire body into a sex organ!
