A couple of changes

Harry continued to thrust faster and faster into his new sex **** and soon felt an orgasm building up. He emptied his load inside Hermione, after which she shakily rose back to her feet. He didn't like the pained look on her face, so he decided to change things around. "'Mione" - Harry said. Hermione's eyes emptied and she stood to attention: "Yes Master" - she said in a flat voice.

"You know that I am your Master, and you are my obedient ****. You love me, love being my ****, obeying me makes you incredibly horny. Being part of my harem full of sluts such as yourself is an incredible honour; you are bisexual and you love all of your fellow harem slaves. You will show this only when you're alone with your Master and/or any other members of the harem. In public, with unaware people, you will simply obey every command I give without a verbal response, acting as natural as possible, as if you're simply agreeing with what I'm "suggesting". Is all that understood?" - he finished. "Yes Master, it's understood" - droned Hermione. "Okay then Hermione, 3, 2, 1...awake!" - Harry commanded.

The change was obvious: the look of shocked concern vanished from Hermione's face, all troubles and puzzlement left behind as she hungrily looked at Harry. Her Master.

"Hello Master..." - she said, slowly and seductively, sticking her index finger inside herself and then licking Harry's cum off of it. "What do you wish me to do Master?"

"Stay in this room. While I'm gone, make your tits a nice D cup for me. Once you're done with that, masturbate non-stop until I come back. But you can't cum until I let you. Do you understand?" - he ordered.

"Oh Master, I certainly understand" - she purred. "Thank you so much Master, I love being your obedient personal whore!"

Harry had a double take for a second, then remembered about his spell and realized all was as it was supposed to be. Now he needed to make his harem powerful. To add slaves. And he knew just the right witch to start the "expansion".