It took Kyle a long time to collect his thoughts. He was shocked by the immense size of his new crab body. The carapace atop which his puny human torso sat stretched behind him 450 meters, and was 540 meters across. He felt his new legs dig into the soil over a kilometer away, and his pincers rested 300 meters ahead of him. Picking one up was as easy to him as moving an arm, and they felt incredibly powerful. However, bringing one to his torso, he could hardly feel his own hand against the massive appendage. He couldn't comprehend how big he had become, but he was forced to accept it.
Looking down, he saw first responders and military gathering around him. Helicopters flew overhead, and he realized he should probably get out of the city before they tried to subdue him. He was, after all, a living natural disaster, a Godzilla monster come to life. He saw a few try to climb on his left pincer as it rested on the ground a hilltop away; they tickled like ants, their bodies tiny and insignificant. Even as they sunk nails into his exoskeleton to mount climbing ropes, he barely felt it. He heaved his new body up instinctively, rising with a massive rush of air. His gigantic legs thrust him over 400 meters into the air, his pincers now resting on their tips.
His head started to spin as he realized truly how huge he was. He took a few seconds to admire the incredible view from his new height. He could see for miles around him, the rolling hills that winded him on childhood bike rides seeming like mere anthills to him now. That is, until he looked to each side. All he could see to his left was his own crab body, same to his right. He realized with a growing horror that he had no idea where he would be stepping, or what he would be destroying. Even if he leaned as far forward as he could, his torso still wouldn't clear the front edge of his gigantic crab body, leaving him blind to his direct surroundings.
Sensing approaching helicopters, he mouthed a quick sorry before beginning his trek to the coast. Emergency sirens blared below him as he took his first tedious steps. He felt the ground shake beneath him as one of his six new legs lifted, and came crashing down some 600 meters to his right. He took another step, and another, his pace quickening. Each step produced a deafening thud and shook the ground hundreds of miles away as his 16,000,000lb weight divided itself between his 6 legs. His claws dragged into the ground beneath him, taking out trees, houses, and power lines like they were toothpicks before he raised them off the ground. Buildings shook and fell as he crabwalked through Glendale. He towered over even the tallest apartment buildings and hotels in town, and his huge legs took them out like they weren't even standing. He barely felt it as he knocked over a 5 story building, then another, and another. If he craned his vision he could see the destruction left in his wake, but he tried not to think about it. He had no choice, with how huge he had become. He still couldn't believe any of this was real, the sun beating down across his massive body as he thundered his way to the sea.
It took no time at all with his kilometer-spanning width, until he felt the cool ocean water lap against his legs. He couldn't relax yet, though, as the water seemed to barely get deeper. He crabwalked for hours, long since losing sight of the coast. Continuing to crabwalk for hundreds of miles, he realized that he'd basically only be able to submerge himself once he reached the continental shelf. Eventually he felt the water deepen, and it lapped against his carapace. He dropped his body down, creating a massive tsunami around him as he left his human torso above the water. The waves crashed against him and washed over him, but he couldn't be swept away. They rippled over his massive body, causing him to act like a living island. This was his life now...
As he sat near the continental shelf contemplating his new form, he realized he had a massive hunger. Underneath the water, his new claws began to feed ton after ton of substrate through his mouthparts, filtering out an amount of small zooplankton and crustaceans that even a blue whale would blush at. It tasted amazing, like the freshest seafood he could imagine, his new body scarfing it down without respite. The curse had made him a generalist, as there's no way he'd be able to feed himself at this size. Even fish weren't safe, as he felt sharks and schools of cod get sucked into his new body.
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Months passed for Kyle as he explored the coast. He waded around, using his massive bulk to his advantage. He stuck to international waters to draw the least attention he could, not wanting to hurt anyone else after crushing numerous houses and destroying millions of dollars of infrastructure in the short trek from Jen's neighborhood to the coast. However, every movement he made caused a record tide at the nearest coastline, not that he could have been aware. He rode out huge tropical storms and hurricanes, hiding under the water as they passed. He was somehow unaffected by sunburns, the curse sparing his human half from frying like a shrimp.
To his surprise, he began to have new, alien desires. He began to feel a desire to incubate his eggs. Her eggs? This gender thing is just so confusing anymore, he thought, thinking about how badly he wanted to protect his spawn. His body also began to feminize, for no discernible reason. His human waist narrowed, and his chest began to ache. He'd let his hair grow long, too scared to try cutting it with his pincers. He'd almost completely forgotten about Jen as he moved around the coast, siphoning local marine life into his crab mouth and basking in the tropical sun. He barely even thought about how he had never felt the need to masturbate since he changed, never even thinking about his genitalia. Little did he know, Jen's sphinx form had destroyed his gonads and feminized both his crab and human halves in preparation for her next step.
She had spent the past few years growing throughout Kyle's body. Her tendrils spread to every inch of his flesh, wrapping their way around his organs and through his muscles. She used these tendrils to siphon energy from everything he ate, for one singular purpose. Her tendrils were her interna, one half of her new hyperevolved anatomy. The other half finally erupted from the base of Kyle's carapace, her externa. She was only dimly aware of anything occurring, the passage of the last few years dream-like, dark, and silent, until she was awoken by a blinding flash of light.
The sun shone down on the water below her. It was a hundred meters or so below, Kyle having wandered a bit closer to the shore for a time. A cool sea breeze whipped against her newly exposed flesh, and she heard the caw of seabirds far above. She saw his reflection; his massive crab body blocking the sun below, but she also saw herself. She had been reduced to a massive yellow-orange blob protruding from the bottom of his body. Her head was facing forward, at the front of this strange mass. She saw his legs to each side, and his pincers hundreds of meters ahead. Days turned to months as she felt her sac expand, filling with her parasitic eggs. Her head and vision pushed forward, inching closer and closer to his pincers and the ground as she hung beneath his body. Everywhere he went he carried her with him, unaware that Jen was hitching a ride. All he knew is that he had eggs to care for; he was a mother, after all!
No longer blinded by her innate need to find a host, she was finally free to feel her own emotions. She wanted to scream, but couldn't. She wanted to cry, and could. Tears streamed down her face, dripping down the huge sac-like body beneath her. In that moment, she would have given anything to wake up from this horrible nightmare. She had no muscles to move. She couldn't even breathe, her throat stopping at the base of her tongue. Over time, her hair grew long around her head, and she had no way to brush it out of her face as the ocean winds blew it around. As the months passed, all she did was use Kyle's nutrients to create eggs, a constant pleasurable heat filling her yellow sac-like body. Her face pushed further and further out, her externa growing huge in its own right. She felt her skin taught, hundreds of square meters of it lapping against the water. She could feel the water rush over her as Kyle swam, or drip off of her every time he stepped out of the water. She swung heavily beneath him as he walked, unable to steady her vision or do anything but shut her eyes. She'd been the star cheerleader, class valedictorian and Ivy League hopeful only a short while ago. Now, years later, she was a parasitic sac of eggs.
Not that she had any idea that it had been years.
Kyle held his pincers around her, protecting her from the rough current. The feminizing effects of Jen's parasitic species weren't limited to the crab half of Kyle. Jen didn't know it, but Kyle had changed her name to Kylie as the changes continued to affect her. Her sore chest had blossomed into a pair of gigantic breasts, which rested against the edge of her exoskeleton as she stood "knee"-deep in the ocean. They started small, but as Jen's tendrils infiltrated them, they grew and grew until each one was bigger than her torso. They were still sore, still growing, the nutrients Jen stole from her feeding both Jen's eggs and Kylie's breasts. Kylie had stolen a few tank tops from a passing cargo container, crushing it like a tin can with her massive pincers, but she had long since outgrown them. Her breasts splayed out on her exoskeleton and reached farther away than her arms ever could. She at first found them annoying, but the tendrils had begun to make her love them.
Jen grew to appreciate it as Kylie protected her. She was careful not to step on anything that could pierce her externa, even as Jen grew to hang over 100 meters below her crab body, spanning 200 meters from front to back and and 400 meters wide. She was herself in shock at how large she had become, filled with hundreds of billions of eggs. She felt her externa sag heavily underneath Kylie's body like some kind of cursed udder, her life reduced to producing eggs and stealing nutrients as Kylie roamed free along the Atlantic coast. Yet somehow, she knew that that was all her body was meant to do. Instinct told her not to worry; that even the amount she was conscious of now was unusual, most of her species-mates had only a few nerves, unaware of anything. She dimly felt her tendrils' simple muscles course through Kylie's body, her sac filling more and more by the day with her eggs. She felt each movement of Kylie's body push, pull, and twist the tendrils, each moment a reminder of how huge they had both become. It felt like a mockery of how little control she had, as she felt Kylie move her legs, or play with her growing breasts. As the sea once again washed over her while Kylie dipped into deeper waters, she closed her eyes and wondered if she'd ever stop growing, or ever be able to talk to Kylie again...