The kiss caught Lilia off guard, but she eager reciprocated. It seemed to go on forever until they both finally had to take a breath.
"I should have told you last night that I was a mermaid " admitted Lilia. "I was afraid because I didn't know how you'd react. I've been in the human world for awhile now, but relationships and trusting humans are still difficult for me."
"It's alright" said Kevin "I understand."
"Will you stay with me tonight?"
"Of course."
They kissed some more then Lilia suggested they move somewhere more comfortable. Kevin scooped her up in his arms and carried Lilia to her bedroom.
"So this is your natural form?"
"Yes, I take a special serum every day that allows me to take human form. That's why I had to cut things short last night at the end of our date - I had to take my next dose."
Kevin gently placed Lilia on the bed and she pulled her dress off, flinging it aside to reveal nothing underneath.
"The thing I like most about mer society over human society is not having to wear clothes" Lilia said with a smile.
Her breasts were pert and perky. Her fish tail went up to her hips, with an unmistakable slit around which her scales glistened with moisture. She let Kevin admire her body then gestured for him to join her. They kissed as they teamed up to undress him. With that finished, he climbed into bed and onto Lilia. They proceeded to explore each other's bodies with their hands as they kissed.
Not much foreplay was needed. Lilia was excited to finally have sex with a human and always found herself a little turned by her transformation. Kevin had a mermaid kink. Both were eager to finally be physically intimate after their relationship's unresolved sexual tension. It was over too soon for both of them and they asleep in each others arms.
---
Kevin woke the next morning to find himself spooning with Lilia and was pleased to find she was still in her mermaid form. From what she had said that would be how she remained until she drank the serum she mentioned.
As he lay there with his mermaid girlfriend in his arms, Kevin recalled he'd woken up the day before under similar conditions, but with a different mermaid. He felt guilty and knew he needed to resolve the situation soon.