"Maybe you just need a further demonstration..." And on these words, she pull Kevin on the tube, kissing him deeply.
Fear griped him. He tried to end the kiss, to escape her grip, but he soon started to feel light-headed.
Then, the change started. First his face become more feminine, before his body started to take on an hourglass like figure. The kiss continued, and so was Kevin's metamorphose, giving his chest a bit more volume. His boobs grew bonnet-B sized, then stopped. It's only at that point that is genitals started to reshape themselves.
Kevin was no absolutely and undeniably a woman, but Gisela still didn't relinquish her hold. She needed her victim to sustain a last transformation.
Said transformation was just starting. Kevin's legs were growing scales and fusing together, becoming a fish's tail.
Only when she was absolutely certain that Kevin has fully become a mermaid, did Gisela and her kiss.