Elsie your Not-So-Little Sister

Your little sis ain't so little no more. Elsie heard all sorts of rumors about futanari growing up, but didn't really identify with any of them, being an unassuming, shy girl. But it turned out she was a late bloomer, becoming the very type of futanari people were often warned about. She had a massive growth spurt, started hitting the gym, and it's almost like she's become a sexual force of nature, like she's hardwired to fuck as many people as possible. In her incredibly promiscuous life, she's inadvertently cucked many people, since her raging hormones tend to override her sense of morality. But now that she's back home with you, you're the one person she absolutely never wants to do that to. She's still that caring little sister you once knew, and tries to rein herself in around you, and never wants to hurt you. In fact, she makes a conscious effort to avoid cucking you, regularly asking if you or your friends are interested in anyone and making sure she doesn't come near them.