"The dog-dicked centaur is in awe of her own semen."
Erin was not sure how the app would interpret this, but decided to try it anyway.
Suddenly she could taste salt in her mouth and she spit. Out came some semen that landed in the swimming pool filled with the rest of Trish's cum.
"I'm so glad you agreed to this," Trish babbled again, "it's been soooo long since I got proper relief. I was pent up like you would not believe. Just look at what you helped do!"
"Yeah no problem," Erin managed to choke out, coughing up some more semen. Looking down, Trish's formerly cantelope-sized balls had grown to beachball sized but it seemed like their size was deceptively small.
"I'm sorry I didn't prepare better, I should have had some paper towels ready for you." Trish apologized.
The knot holding them together was dying down and Erin wriggled off, spilling some more cum as she stood up. She decided now would be a good time to generate a new sentence.
"Erin is finaly free of the rainbow centaur's dogdick."
She absentmindedly changed "free" to "part" and accepted before she realized what she had done. Reality twisted around her and the sentence was now true. She looked around. She was inside a barrel of some kind and was knotted by Trish again.
"Alright, I can feel the knot is going down, pull your arms in." Trish said from above her. Her previous assessment was wrong. She wasn't knotted by Trish, she was Trish's knot! She held her arms forward, phone in hand, as Trish backed up from the barrel, bringing her sliding through the slick lubricated padding lining its walls. The barrel was a plastic drum tied down to two wood sawhorses.
"That was a great session Erin. I can't believe how good that felt, we made so much cum. You make an awesome cock!"
It was true, Erin could feel a pride deep in herself at having handled that much semen.
"Was that better than you expected? Did you think that would happen when you agreed to be my dick?"
Some memories came unbidden to Erin's mind. Trish had been working on getting Erin to agree to this for months. Finally she caved and they made a trip to the conjoinment clinic. Today was their first day back.
Erin looked around for more changes. Her phone was the same model as before but now had a heavy duty waterproof case. Her legs and horsecock were now gone, and her hips were replaced by canine knots.
"Speechless huh? It was pretty mind-blowing. Anyway I'm going to drain the pool now."
Erin coughed up a bit more semen which landed on the floor. Oddly it felt good to expel it, maybe she could get used to this.
Trish heard this and scolded her, "Erin! Try to get it in the pool, we'll have to clean that up."
Erin collected herself enough to speak. "Sorry I'll keep that in mind. Yeah it was fantastic, I can't wait for next time."
It seemed the conjoinment clinic had done its job because Erin was not straining at all even though she was planking by any other measure, breasts swinging freely below her as her host took them to the pool controls.
"Haha yeah. First things first though, we need to take care of business," Trish said.
"Business?" Erin questioned. With dawning trepidation she realized what the sensations of pressure coming from inside her host meant.
"Yeah, we've gotta piss like a race horse."