She tries to leave

"I don't have to fucking sit here for this," Maxy said, leaping to her feet. She took a glance at her sister's soaking pussy, shaved, fully on display with a cock she knew all too well entering it. Yeah, fuck this. There's no way Curtis would tell the kids anyway. She turned to leave.

"Stop her," Curtis whispered in Luna's ear. Sure, there were things he could do more directly to get her to stay, but this would be more fun.

Overwhelmed by desire, the only thing Luna could think of was to say, "you can join us." She gasped it out, a momentary declaration, splitting her cries of passion. She said it softly, as though it was the most she could manage, but honestly.

It seemed that she had heard her sister, though, because Maxy stopped in her tracks. She turned around, slowly, as if moving normally would give something away. "What did you say?" she asked, voice flat.

It took Luna a few beats to respond, gathering her thoughts. She pressed back against Curtis again and again, and he seemed content to let her do the work. She fucked him harder and harder and her pleasure grew. His cock sent a shock through her each time. "I know you want to join in, Babe. I know you want me. If you stay you can lick my pussy." She sees Maxy hesitate and knows that she has her. She hated herself for doing this, but she'd do anything to keep their secret. Besides, how much better would this be if she was getting her pussy licked? "This is the result of your slutty ways. You fucked your sister and you've been caught. Now you have to slut your way out of it," she said, relying on their old role playing. She'd said something almost exactly like that last time, and she couldn't think clearly enough to come up with something new. The difference was, this time was real.

Maxy scowled, but it was obviously performative to the woman who shared her face. Her sister slid down until she could watch Curtis' cock entering her and gave her pussy a lick. Usually Maxy would go for parts of her that were inaccessible at the moment, but she knew how to make due with what she was given. Maxy used her tongue on both the cock and Luna's clit, sliding from one to the other as if they were one organ.

Curtis felt his cock twitch at that, though her tongue felt hesitant to him. When he'd made Luna irresistible, he didn't think it would be so literal. He doesn't mind too much, though. Mostly he just couldn't believe he had his ex wife licking his dick, he couldn't believe she looked like a young porn star, and he couldn't believe the irresistible goth look-alike was riding him like it was the only thing that mattered. "Tell me before you cum," Curtis commanded Luna.

The three continued like that for a while, with Luna riding him and moaning, Maxy pleasuring the two with her mouth the whole time. She showed no signs of losing interest, and instead seemed to gain more enthusiasm as she went. She cupped her sisters prodigious ass, as if helping lift her up. Instead, it was clear that Maxy simply fucking loved Luna's amazing butt. The sexy teacher didn't leave Curtis dry either, licking her sister's slick off his cock like ice cream.

Eventually Luna shouted "I'm gonna cum!" in the middle of a bout of "'oh yes' and 'oh God!'" The moment she did, Curtis stopped everything. He shifted his weight to cut off access to his dick, wrapping his arms around the woman. He let himself cup a feel of her tits while he did.

"Wh... what?" Luna asked. "No, I was gonna cum. Keep going!"

"I promised that I was going to make you my bitch," he said, calmly. Inside he was screaming to keep fucking her too, his dick only barely penetrated the woman. Every instinct in him told him to shove it into her. "I want to hear you say it. Tell me you belong to me and I'll let you finish. Be honest and admit that you want me even more than Maxy and I'll fucking you until you cum over and over again. Otherwise we stop here and you can leave." Curtis thought for a moment, before pulling the silver ring off his wedding ring finger. He knew he had her. "I'll tell you what, if you leave, I'll throw in this new ring. Take it as a sign of my blessing for you two's relationship."

Curtis thought he could make a copy of the ring for the Museum with his powers, not knowing that he has nothing without the ring.

A/N: Poll time! I have some ideas for where to go with Curtis (spoilers: the Museum owners are up next, as well as some creative uses for the Museum exhibits), but I thought it could be fun to have Luna take over from here as well. Vote here for which of these will become the main branch: https://strawpoll.com/polls/PbZqoDXMKnN