Her body looked fine, but there was still something odd. Managing to sit up after a few more tries, her head pounding a little from sleeping in a little too late, her indigo eyes blinked, trying to clear themselves of sleep. The headache was a bit more intense as the blood rushed from her head, and her breathing was a bit shallow. Whatever she had done the night before must've taken quite a toll on her body, as her arms were shaking and her skin was quite a bit paler than usual. Nothing that she couldn't have really brushed off.
Except the sound.
Rika's ears perked up as she caught a low rumbling sound, akin to distant thunder or a low jet in the distance reverberating throughout her weak body. It shook her flesh down to the bones, sending her skin crawling with goosebumps, a shiver running up her spine as it started to build. Her blurry vision was straightening itself out as the sound became louder towards her middle, thin hands pressing against the sides of her belly as her eyes widened with shock. Letting out a soft grunt of discomfort, her middle began to groan deeply, like the sound of flesh stretching, and her body began to expand. Her belly starts to pour through the gaps between her fingers, growing with thick adipose as it's the first thing to start swelling from this strange reaction as it quickly turns into a butterball in her hands, swollen up with new mass as it rests heavily in her lap.
"W-what...what's happening...?" Rika managed to get out, her voice caught in her throat by the suddenness of the oncoming change. Her thighs plump up, her night dress snug against her fattening form, even her fingers porking up as her 11-year-old body is overcome by this wave of blubber that just seems to grow larger with every passing second. Gripping the bed as she began to round out, her chest even porking up and giving her a little early development, her body quickly surpassed that meager 70 or 80 pounds, plumping up into a fit and healthy 90, before plunging into a rather chunky area for a girl of her physical age. 100, 110, 120 all passed within a few minutes as she watched, entranced and horrified as her body porked up, rolls forming on her belly and her thighs swelling with fat. The bed creaked and groaned as the blunette fattened with abandon, easily three times her original weight if not more, her stomach folding over into cushy rolls while her arms quiver and quake with blubber, the feeling of new cankles almost surreal to her as they rest atop her fattened feet.
It was over, almost as quickly as it began. The quaking of her fat settled as the groaning vanished, the sound of stretching flesh disappearing as her body peaked out at its optimal weight...for now. Breathing shallowly, watching her meaty chest and belly rise and fall with every cycle, she groped her gut's swollen, round and rolled surface with plump hands, kneading it to verify its existence.
"W-what....w-what the hell is happening...?!" Rika gasped after a while, her cheeks and second chin quivering a little thanks to how full they had become. Before she could get her thoughts together, however, her processes were interrupted by a knock at her door. Quickly assuming her younger persona, she squeaked a little, hearing how her voice had gotten a little deeper. "M-Mii! W-who is it?"