Cement your changes

Your sister's hole is a fountain. Overflowing with juices. You poke your mushroomed head up to the entrance.

"MMMmmmm, Master please, just fill me." She says begging through the pillow, head turned to see with one eye, her hands moving up to spread her cheeks. The warmth wetness sends jolts through your member. Craving these feelings, you begin to push. Getting the head in takes some effort but once it's in.

"Oooooaaaah! Yesssssss." Kim shrieks.

"Here comes the rest, You feel so good." You say pushing slowly but without stopping delving your cock deep into her.

"Fuck! Your so deep. So much deeper than Brad." Kim breaths out. Brad was her boyfriend, he was an okay guy. Never mean to you or your sister. But you two never really got along. You read comics and played games, he wrote and acted. Your worlds never really connected. But now you have to do something about him. Given that Kim was to become yours, it would become awkward. "Sorry Brad I have to go home my sister wants me to fuck her giant cock. See you tomorrow!" You could just imagine that being said. Kim was smart but with what changes you have implemented that sort of precaution could be thrown to the wind.

Your thrusts are slow but powerful. You keep a steady rhythm while having one hand hold her ass the other thumbing her ass. You lean down toward her head. "Now Kim, what do you think of Brad?"

"He is, was? My boyfriend, his cock never compared to yours. I only dated him because he was nice to me and kept other jerks from trying to constantly sleep with me." She says with labored speech between moans and shocks sent through her body through your constant ramming.

"What does he know about our relationship?" You ask inquisitively, speeding up but not going as deep. A punishment as far as Kim is concerned.

"He doesn't know that your cock is huge. He doesn't even know you have one. As far as he is concerned you are just the sibling across the hall." She says slightly pouting wanting you to return to your relentless ****.

"Keep it that way. Kim, He is to stay out of our way until the time is right." You order, suddenly plunging deep into her.

"OH GOD! Yes sir!" You say, continuing your ****. After a few minutes and multiple orgasm on Kim's part. You begin to feel the orgasm building in you. Your speed has been slowly increasing as has your aggression on her. Spanking, sinking multiple fingers into her ass. Out of the corner of your eye you see her hands start to return to flesh color. Your **** will finally be converted fully. Meanwhile your red suit is still glistening in deep crimson.

"Kim, I'm going to finish inside you. You will be mine. As you have always been."

"Yes Master! Please, mark me with your seed. I'm on the pill so please fill me!" She moans. After she says that a flood of sperm. Unloads into her. After a few moments your cock is almost **** out due to the shear volume in her. You pull your member out and release yourself from her ass. An audible pop is heard as she gapes, and leaks your sperm onto her sheets.

You fall back onto her bed. Your dick hard as ever dripping in various fluid. Looking over her she is slowly becoming skin tone by the second. You want to wrap it up though, so you go over to her mouth. "Clean me bitch."

The instant you say that her eye's burst open, crawling over and licking you all across your shaft. Sucking your head for what sperm she can save. Pinching her nipple you notice it turn back to the dark brown you would have guessed. After a few moments. She is back to her skin tone self. The only difference being that she is still suckling your cock like the breast of a mother to a newborn. Now a question comes to your mind. You know that you have time to get your brother with your red suit. But, what will your sister do in the mean time. Lend a hand in taking him? Maybe you gift her with her own black suit. Let her recreate herself to an image you would find appropriate?