"So you need to get me off to change back?" asked Ethan.
"The calendar was supposed to be for you, and I think the transformation is as well" said Ava. "I suppose it’s good that you do like it, otherwise I might be stuck this way."
"I do like it; I like it alot" admitted Ethan "but I also like not dying in a car crash because I'm distracted."
"Pull over up here" said Ava as she tied her hair back.
Ethan pulled off the road into a shaded area facing away from the road. As soon as the car was in park, Ava unzipped his fly. Ethan reached over and felt Ava's scales again and she shuddered at his touch.
Ava kissed Ethan briefly. "Lets not do this in the car next time, okay?" she said. Then her mouth was full. Other than one hand on Ava's scales, Ethan left her alone as she worked his erection with her tongue. She started with the tip, but slowly worked her way down. Soon Ethan had a death grip on the steering wheel with both hands, trying to hold back as long as he could, but after a few minutes he was finished. Ava thought for a moment about rolling down the window and spitting, but the salty taste was strangely enticing to her as a mermaid and she swallowed instead.
Ethan and Ava sat there for a few minutes as their heart rates slowed. Ava soon found herself absentmindedly running her hands along the scales of her mermaid tail. Her tail seemed no closer to going away. Touching her slit, Ava found she was wet.
Ava looked at Ethan and found he was watching her intently. Ava thought back when she had first transformed and found the card accompanying the calendar. She woke up transformed after being aroused by an erotic dream. She passed out, had no further erotic dreams, and woke up with legs.
"Dammit" muttered Ava.
"What's the matter?"
"I think I misunderstood the consequence clause. I may be transforming for your benefit, but it happens when I'm aroused, not you."