'You know, I have an idea,' May giggled. 'How about we turn a... brother... into a sister?'
Misty looked incredulously at her, then she realized what May meant: walking along the beach, alone for once, was Ash.
All three mermaids began to sing to him, slowly but surely drawing him in. 'Come on, Ash,' Misty purred. 'We're gonna show you a better life.' With that, she began to kiss him- reluctantly, given how rough he felt compared to her sisters. He removed his clothes and Misty pushed him to the ground naked.
The three of them looked over him confusedly. 'Wow... he's so weird,' Dawn murmured. Misty pressed the Water Stone into Ash's hand and he began to rapidly change. His hair turned blonde and lengthened down to his hands. His hips started to flare out and his waist shifted inwards. His small confused moans turned higher-pitched. His chest started to swell out into D-cups covered by a red bikini.
'Wait a minute,' May said suddenly. 'He's not changing down there, is he?' Misty shifted the Water Stone from his hand to rub his crotch and legs with it. His manhood started shrinking and shrivelling up inside him until the space was clear, and her legs melded together into a black-scaled tail. As she came to her senses, she murmured, 'What happened? Misty?'
Misty smiled excitedly at her. 'Oh, you'll love this,' was all she said before launching herself at her, driving both of them under the water. She pulled off Ashley's bikini and suckled her breasts, making Ashley moan loudly. As she pulled her own bikini off, Misty moved up to loop her tail around Ashley's. Both of them convulsed with pleasure, Ashley biting her lip to keep from crying out until she eventually came, feeling her tail fins spasm with pleasure. Misty, too, moaned excitedly and deeply kissed her, both of them letting out excited cries into each other's mouths.
As they surfaced, Ashley grinned. 'Th-that was AWESOME!' Misty got a warm feeling in her chest from having made Ashley enjoy it so much.
'So, who should we go find next?' Dawn asked.