That night, after Becka went to sleep, Maria slipped on her fluffied socks and gloves to mute any sound she made, and slunk into her little sister's room. In one hand she held the drainer from beneath her bed, which she carried almost like a religious artifact. As she removed Becka's primary device, the bed shook a little, but her little sister paid no attention, sleeping through the jostling. Maria replaced it with the device from beneath her own bed, and snuck back to her bedroom. She set the device to drain #1 (the one now beneath Becka) entirely, and then decided that since her mother was useless, there wasn't much point in leaving her some attractiveness. She set #2 to drain completely as well.
Becka had purchased these devices from an old scientist, a partially crazed if chivalric man who listened to her (totally fabricated) sob stories and gave her the devices for $5 each. She hadn't bothered with why they worked; only that they worked. What she should have noticed, had she not been so busy taunting her family and seducing boys, was that her growth remained constant. Anyone with half a mind would expect Becka's growth to skyrocket during puberty as she drained her family and began to sprout herself.
Of course, almost the exact opposite occurred. Because she had entered into a cycle where her own body grew rapidly, most of the size and beauty she stole was relegated to be stored inside of her, packed in small clusters of fat cells. Essentially, her own growth denied the stolen growth, but since it was being forced into her body, her anatomy responded by storing it.
Maria lay awake, waiting for the changes to take hold. Her puberty would not have ended until 21, but Becka had sucked all of the growth from her. Therefore, she had nothing natural to interfere with the artificial growth. Maria looked down at herself as she began to feel a tingle, and saw breasts swelling beneath her shirt. She could feel her ass pushing her hips further away from the bed as it expanded and tightened. Her skin took on a healthy glow, and then she felt herself inching upward. She had set the device to perform a complete drain, so it was taking all of the height that Becka would receive through natural puberty.
In her room, Becka tossed and turned, assaulted by nightmares of never having met that old man, in which she was still 4'10" but had no body whatsoever, and her sister stood beside her, a six-foot-tall goddess. As her body shrank in real life, her breasts and ass dwindling, her lips losing their sexy pout, she dreamt that suddenly Maria started growing even taller and sexier. The dream grew more and more terrifying, until Becka hit a breaking point: she then found her goddess sister unbearably sexy, and began grinding against Maria's leg as her older sibling continued to grow.
Becka moaned, her hand sliding down to her lower lips even as her body dwindled, a huge smile spreading across her face as she worshiped her growing sister. In her dream, Becka was constantly cumming just from looking at Maria, as was anyone else who saw her. That meant that more than half the planet was in a state of continual orgasm, since Maria was larger than Earth.
Maria stared at her breasts, too entranced to even touch them as they grew ever outward, having long surpassed even Becka's prodigious pair. They just kept growing, perfectly firm, stretching toward the ceiling and walls with a determined cadence of expansion. If she had to guess, she now stood over six feet tall, and her titanic ass stuck out for what felt like miles behind her. Her legs were long, toned and gorgeous, and her voice was so sexy that even hearing just her subdued moans caused her to release a quick burst of cum. Her own voice made her cum! Maria was still wrapping her head around that one.
As Becka's body deflated to nearly nothing, her stores of stolen beauty were running out. Now, more so than before, her own puberty was being tapped. If Becka had just waited for nature to take its course, she would have been well rewarded. Her sister was destined to grow into a beauty of model height and porn star proportions, but Becka would have surpassed Maria in every way. She would have grown to 6'9", with a huge ass and H-cup breasts, with a face so gorgeous that every company on earth would want her for their ads. Now, though, she was even shorter than she'd started - only about 4'4" - and all of that potential for beauty was flowing into Maria and being made real.
What happens next?
(a) Maria finishes draining her mother and sister, and decides to drain some of Becka's friends, who are just about to enter puberty as well.
(b) After Maria drains them, she finds that she's also somehow absorbed the capabilities of the devices. She can drain people just by willing it.