If you think about it, there were indeed cats in fairy tales, except that they were mostly black cats sitting on an evil witch's shoulder. They were gloomy and scary, and often terrified the fairy tale heroes with their long, sharp teeth.
Fina's tone and face were both provocative and tempting. It showed its little tiger's teeth once in a while, looking slightly like an evil black cat in a fairy tale.
It placed a seemingly impossible trade in front of Sihwa––trading her tail for a human's identity.
Yet, the trade was not totally impossible; it was actually kind of feasible.
If Sihwa really showed up to the world as a handicapped girl who had lost her legs, nobody would ever think that she used to be a mermaid. She could get as much sympathy as she wanted by using her gorgeous face. It was hard to get an ID card, but not totally impossible. There were many things one could not buy with money, but an ID card was not one of them.