You help your son get laid.

You keep on watching Diah suck on Rowol’s dick while Rowol moans and caresses the fleshy part of Diah’s Lethorns. But then you feel the time is right for your son to become a man and you use your mind trick on Diah again.
“You want to have sex with him.” You command.
Diah pulls her mouth off Rowol’s dick, sucks her long tongue back into her mouth and says, “I want to have sex with you?”
Rowol, in happy surprise asks, “Really?”
You then mind trick Diah again and say, “You want to ride him.”
“I want to ride you.” Diah repeats after you.
The purple skinned girl then stands up and pulls her shirt off. Rowol doesn’t waste any time and quickly pulls his pants off for Diah. Then you watch Diah take off her pants for Rowol and mount him. She helps him take off his shirt and then both teenagers are nude on Rowol’s bed.

From where you stand you can watch both of their genitals. You can see Diah grab Rowol’s dick with her left hand and point it straight up. She then brings her purple pussy right above it and with her right hand she pulls her pussy wide open. Rowol himself has both his hands on Diah’s hips while his eyes stare at his girlfriend’s hungry pussy. Then she lowers her hips and lets her pussy engulf his dick. Watching your son’s erect dick disappear into this young chagrian’s girl’s cunt puts a smile to your lips. Rowol has no idea how awesome a dad you are.

At first Rowol and Diah are moaning and groaning a lot. This is probably the first time for both of them so the novelty of everything is washing over them. But then Diah gets into a proper rhytm and starts riding Rowol.
“Oh, wow.” Diah says. “When I agreed to come here, I thought we would just be making out like usual. Not that it would be like this.”
“Yeah, me too.” Rowol says. “I did not at all plan on going this fast so quickly.”
“You don’t mind I hope.” The purple girl on top of his jokes.
“Not at all.” The human under her smiles. “I’m in fact very happy with this all went.”
“Me too.” Diah says as she smiles back. “I love you, Rowol.”
“I love you too, Diah.” Rowol replies.

For the next few minutes, you watch the two teenagers have sex. You watch Diah bounce on Rowol’s dick, providing you a beautiful sight of her large boobs bouncing up and down. Since neither of them can notice you, you take the moment to feel up Diah’s boobs yourself. Her purple tits feel amazing in your hands. Too bad the boobs on both your wives are smaller than hers. You would have really enjoyed a wife with boobs as big as Diah’s.
As Diah gets closer to orgasm, you notice her riding your son faster. She moans with every breath and grabs her lethorn at the horn part to pull on them. For a moment you imagine her as a human girl with her lethorns being like really long hair in twintails. But that would be mundane. As a chagrian, her lethorn look a lot more exotic.
All of a sudden, Rowol calls out to his girlfriend, “Diah! I’m gona cum!”