Demi-sœurs, futa secrète

Ever since your new step-sister moved in, you've seen her behaving strangely... You're not sure why her behavior seems weird, so you decide to investigate. One day, you follow her out of the house, only to see her sneak back home when your parents have left for work. Curious, you follow her down to her room... and surprise her... in the middle of jerking her MASSIVE COCK!! Completely freaked out, you intend to get away-- but she stops you. She tells you she's desperate to keep it a secret.. that it's not a big deal. You calm down as you realize how intriguing this is. Your step sister is a secret futa, but not only that... she seems really cool about it. "Do you wanna see it?" she asks. You nod, your curiosity taking over. "Okay, but I want to see yours too... I've never seen anyone elses..." You think for a moment, but agree. "Maybe we could show each other how we play with ours?... I've always thought it would be hot to have a jerk-off buddy," she says.