So, this is what it feels like to be hit with a Rasengan, Sakura thought faintly, lying at the foot of her hexagonal crystal pillar in a pool of her own blood. Surprisingly, dying didn't feel nearly painful as she thought it would.
Perhaps it was because the rotational forces had twisted her neck a full three hundred and sixty degrees, snapping her spine and severing her brain stem, but she couldn't feel a thing below it. It was probably for the best, since her body had taken almost the full brunt of Naruto's Big Ball Rasengan. Her chest cavity had been torn open, revealing her organs pulped and streaked with fragments of her rib cage— and that red‑and‑white lump by her feet… was it her imagination, or was that one of her breasts?
Sakura's vision grew dim. Her thoughts were fuzzy; she couldn't quite remember or understand what was happening to her. It was a testament to the resilience of her life force that she hadn't died immediately upon contact…
"Onee-sama…!"
A girl's voice echoed distantly in Sakura's ears. Something salty that tasted of iron wet her tongue, but the fluid slipped out of her mouth.
"It's no use, her throat's been crushed," a man's voice rang out, muffled. "Focus your healing there while I turn her head back on right."
Sakura blacked out...
"Hold her still!"
…and woke up screaming from the sheer agony wracking her body, the pain coming in rolling waves, from the tips of her toes up to the crown of her head. Kakashi seized her wrists while Karin forced her blood down her throat, and instinctively, Sakura swallowed.
"Sakura-chan!" A mini-Katsuyu cried in her ear. "You must open the Yin Seal! The Hundred Healings! Quickly!"
The fact that Sakura felt pain at all was a sign that the nerves in her neck had successfully reconnected. Now that her head was on the right way around, with no extra turns, the Celestial Lotus Seal's power could be sent to the rest of her body!
How much of her lifespan would be consumed to repair this much damage, Sakura briefly wondered? Still, she thought to herself in a flicker of clarity, she had no choice but to use Lady Tsunade's ultimate kinjutsu. Even with Lady Katsuyu's healing mucus and Karin's healing blood, she would die at this rate, with her mush of internal organs hanging out for all to see.
"SAGE ART: ORGANIC REINCARNATION, ONE MYRIAD HEALINGS!"
Bone shards flew out of her chest cavity like popcorn as her insides writhed and wriggled, her internal organs reforming rapidly. Connective tissues joined together, muscles knitted themselves back together, and skin closed…
"Sakura's… shrinking?" Kakashi said, startled.
Before Katsuyu's, Karin's and Kakashi's mystified eyes, Sakura's body started contracting, her limbs thinning and shortening and her muscles losing definition; everything but her newly regrown chest was shrinking. She had lost too much blood, too much flesh, that even senjutsu chakra couldn't replace it all, but most importantly of all…
"This isn't Tsunade's Mitotic Regeneration!" Katsuyu gasped. "My goodness! I haven't even taught it to her yet, but she's already instinctively using the Honoured Sages of Shikkotsu Forest's speciality, Organic Reincarnation! She's remodelling her body!"
Most importantly of all, Sakura had no wish to end up a wizened old crone while still in her teens through overusing the Hundred Healings. However, unlike Tsunade's Yin Seal, Sakura's Celestial Lotus Seal was infused with senjutsu chakra, so she was subconsciously reversing her own ageing even as she mended her shattered body on autopilot.
"She looks no older than she did out of the Ninja Academy," Kakashi said worriedly, as Sakura's eyes began fluttering. "Is Sakura going to be all right?"
At her newfound size, Sakura was nearly as round in the chest as she was tall. Would she even be able to stand up and fight, or heal the villagers?
"Listen to me, Sakura!" cried Katsuyu. "You must use the spare organic material on your chest to restore yourself! You're instinctually using Organic Reincarnation to heal yourself, but once you wake up, you'll be stuck that way! Do you really want to stay as a little girl? You won't be able to protect your comrades in this form!"
Katsuyu's words reached Sakura's subconscious mind just as she was about to wake up.
She was operating on instinct while unconscious, which meant that once she woke up, she'd forget everything, and she'd have to train under Katsuyu in order to properly learn Organic Reincarnation and age herself back to normal.
Sakura stirred fitfully in her sleep.
Being young was nice, but there were many things she wanted to do, things she could only do as an adult. Her body began to grow again, her immense breasts quivering and shrinking as her frame lengthened, until she had surpassed her normal height. She now stood at 175 cm tall, but her bust had deflated to a mere 110 cm, a modest J‑cup, smaller than she had been in years… and that wasn't even taking into account the increase in size of her rib cage proportional to her new height. In her youth, Sakura's band size had been 30 inches. At sixteen, this measurement had grown to 32 inches, and now, standing at 175 cm tall, it was 34 inches. Her new 34 J-cups were the equivalent of 32 K-cups in volume!
Sakura's eyes flew open, and she sat up with surprising ease.
"Kakashi-sensei? Karin-chan?" she said, looking around blearily. "What happened? The village…"
Her eyes widened in shock. "My boobs!" she yelled, palming her bust.
"With Minato-sensei's help, I managed to defeat Deidara," Kakashi replied tiredly. "Lord Second and Third are duelling Hoshigaki Kisame, but Madara is proving difficult to take down, especially now that he's turned tail and run… still, the situation over there is under control, so we came here to help…"
"…Casualties?" Sakura whispered.
Kakashi shook his head wearily.
"I'm not sure… most of the civilians are gone…" he said dully. "Jiraiya-sama and Guy… confirmed dead. Orochimaru is missing, but the four Hokage are still fighting, so I'm not quite sure what to think..."
Still in convalescence, Jiraiya and Guy had been vaporised without a chance to fight back when Deidara started dropping plastic explosives.
"What about the Pains!? We were just fighting them!" Sakura gasped in realisation. She looked around wildly, but there were no traces of them nearby. "Where are they!?"
The ground suddenly trembled, and the very air shook as something inhuman howled.
"Over there," Karin said, raising a trembling finger. "They're still fighting."
Sakura's pupils contracted, and she shook with visceral fear.
"Six, seven, eight… nine tails…?" she whispered.
Two monstrously tall figures were fighting in the distance. Evidently, the Nine-Tailed Fox had completely taken over Naruto's mind. Why wasn't the Fourth Hokage's chakra imprint sealed within him doing anything to stop his rampage? Why was the beast attacking Sasuke's Susano'o!?
"They thought you were dead," Kakashi said quietly. "We all did… except for Karin."
Sakura tried pushing herself to her feet, legs trembling.
"Onee-sama, you can't!" cried Karin. "Not in your condition! And we need your help to heal the survivors!"
"I'm just going to show my face a little," Sakura said, pink chakra enveloping her body as her Susano'o formed around her, lifting her up into the air. "Stay here, I'll be right back."