Picture by tokki
"Look, babe!" Kate exclaimed, picking up a perfectly symmetrical white clamshell and showing it to her boyfriend, Ellis, who was napping on a nearby towel. "Lemme see," he said, sitting up and holding out his hand to examine the shell. As she handed it to him, he realized that it was too light, something Kate didn't notice. "Sorry to break it to you," he told her as he handed it back, "But I think it's plastic. Maybe it was some kid's toy." Kate looked at her shell in a new light, weighing it in her hand and realizing he was probably right. She turned to put it back as Ellis lay back down, sleep returning to him. "E-Ellis," Kate's voice came, a fear tinged it that set off alarms in his mind. His eyes shot open, and he leapt up, worried something was wrong. He found her clasping her chest where the shell was affixed to her breast.
"What's happening!" Ellis asked as Kate kept trying to pull the shell off her skin. "It's not coming off!" She panted as Ellis realized her body was shrinking, "And now there's another one!" He noticed the identical sahell adorning her other boob, giving her a clamshell bra. Ellis stood back in shock as he watched his girlfriend dwindle in size, no, she was being sucked into the shells. She looked up at him, now finally discovering that she was significantly smaller. "Help me!" She flustered as more and more of her was pulled into the bra. The last of her body was pulled into the bikini top, letting it plop onto the sand in front of Ellis.
He stood there for a few minutes, unable to process what had just happened. When he finally came to, he shakily reached for what was left of Kate, picking it up. He held his girlfriend for a moment before the bra came to life, leaping at him and wrapping around his bare chest before he could react. Searing pain flooded his body as Kate adhered to him, a glossy film crawling up his skin from beneath it. Panic set in as he tried to tear his transformed girlfriend from his chest, but instead the change sped up as if it sensed his desperation. "W-what the hell!?" Ellis exclaimed as more of his flesh was turned into what he was quickly realizing was vinyl.
Horror crossed his face as his chest began to expand, filling the woman-turned-bra with rapidly plasticizing fat. The endless crawl of the transformation kept at it, narrowing his waist before reaching his hips, where it caused them to widen. His butt grew in size to give the alluring figure of a peach bottom, but without the warmth that was removed by it being made of polymer. His legs stopped listening to his brain, violently closing together under the command of the creeping plastic. Ellis stared wide-eyed as his legs fused together, taking on a blue hue with a scaly texture. His feet flattened and grew wide, completing the new tail he now possessed.
"I'm becoming a mermaid," Ellis said, defeatedly, "I'm becoming a fucking plastic mermaid with my girlfriend as my clamshell bra." He laughed at the absurdity of the situation, only to stop himself from crying. Something that would've been literally impossible to believe was happening to him, and all he could do was accept his fate as his face took on the plastic sheen, reshaping his face to be cute with wide blue eyes and a seashell choker. A tear slipped from his eye right before the duct fused shut, rolling down the curve of his breast and falling into the sand, instantly disappearing. A rock rose from the beach, forcing him into a sitting position like a siren calling sailors to their doom.
He shrank to the size of a figurine, dropping silently onto his towel with nothing to do but wait for his new owner to find him.