Chapter Text
Naruto's plan to surprise Kaguya and land a hit on her was his Sexy-Jutsu.
Sakura barely had the time to despair.
A white bone stabbed through the true Naruto. Unsurprising, considering that she had seen him perform his Kage Bunshin and could easily track the original.
Sakura saw Sasuke attempt to attack anyway, and Naruto start to heal, only making his dissolution a bit more protracted.
And then, The original Naruto plummeted into the lava, and after a second, all of his constructs that were holding everyone aloft winked out.
Sasuke summoned his Susanoo, and Kakashi-sensei controlled his descent to get closer to Sakura, then gave an expertly executed kick. It broke half of Sakura's rib-cage, but it also sent her arching upward. At the price of having him fall even faster.
Sakura had almost finished healing herself by the time she hit the stone ceiling. She hurriedly stuck herself with chakra, ignoring how the hot stone was already starting to cook the sole of her sandals. She wasn't about to waste Sensei's sacrifice.
Or...
Sensei wasn't at the same place.
Her eyes tracked to Kaguya, only to see a Kamui spiral bloom above and behind her. Underneath, Obito splashed into the lava too. He had used his eye to save Kakashi. Probably a bid for redemption.
It wasn't enough. Sakura knew that even as she launched herself toward her enemy.
Kakashi attempted to stab the goddess and was skewered and strangled in her hair instead.
Sasuke lurched back from the shock-wave, and his Susanoo fell on it's back into the lava, sanding molten rock flying everywhere.
Sakura too was hit by the shock-wave.
It nullified her forward momentum, but she didn't have to worry about falling to her death for long, because the lava surged up to her from Sasuke's fall instead.
One good part, she mused, was that with how hot lava was, pain receptors were cooked before they could fire.
She was missing the entire right part of her body, but she wasn't feeling anything.
She still had chakra in her Strength of a Hundred seal. Releasing it would regenerate a good chunk of the damage. Which would enable her to... Probably die in a couple of seconds more, being honest.
She was a Shinobi. She should die fighting.
"No. Keep it, you will need it."
Sakura flinched. She was no stranger to voices in her head, but this wasn't Inner's voice.
By the time she had recovered from her startled pause, the damage to her body was so extensive that she knew that even emptying her seal completely wouldn't restore her.
She chose to heed the advice. It wasn't like it would make much of a difference, in the end.
The last thing she saw as she was consumed by the lava, was Sasuke's Susanoo winking out of existence in her peripherals.
They had lost.
Sakura had pretty standard expectations about what should happen after her death.
It was either the Pure Lands or nothingness.
Definitely not this... Whatever this was.
She was floating on water, and around her, grays blended into each-other.
She straightened gingerly and looked around. At one horizon of the plane reigned pure white, and on the other side, pitch black. She would think it some sort of yin-yang metaphor if not for the way the black was creeping over toward the white, encroaching more and more.
Sakura got to her feet and took a moment looking at her perfectly healthy limbs. A bizarre development when she knew that there wasn't much left of her by the time she actually died for real.
Well.
It could be more weird.
Years of having Inner in the background had somehow attuned her to understanding when a body was in fact pure yin chakra.
That's what this body was. A projection of self. Not an actual flesh and blood vessel.
Just about everything she had heard about death would urge her to go toward the light. So with nothing much to do and no better option, she started walking.
She didn't walk very long. The creeping dark was a good way to gauge this.
Up ahead, she saw a form, which resolved itself into an inhuman looking old man.
She was cautious at first, especially with the striking resemblance to Kaguya. But Naruto (a pang of pain went through her heart) had spoken about an old man who was Kaguya's son and was the Sage of Six Paths. So she gave him the benefit of the doubt and kept walking toward him.
"There you are, child." The man said when she drew close. "The last hope of a dying world."
Sakura blinked in surprise. "The last hope? How?"
"There is one last thing I can do, to hopefully let the world find another conclusion. It has to be done quickly. Before all of the power here dissipates." With this, the old horned man gestured at the darkening sky.
Was the light a representation of power? One that Kaguya was snuffing out with the world tree?
Well. She was dead anyway. "What is that last thing?"
"Something I have never done before. The force required would be too big, and the reward not enough. At least until now. I am proposing to send you back in time, before all of this, so you can rectify the course of history."
Sakura considered those words, and then the fact that she was the one standing in front of the Sage, no one else.
"You propose to send me back in time?" She asked incredulously. But really, regular logic didn't seem to apply anymore. She had seen what Madara and Kaguya could do. Why not go to the past, after all? "How far back?"
"Ideally, to a time where you can live out the entirety of your days before the current you was even born." The Sage answered simply.
She frowned and did some quick math the entirety of a natural lifespan would put her... Before Konoha was founded.
"Why? Why so long ago? And why me? I am not one of the important people. I'm not Sasuke or Naruto." She argued weakly.
The Sage lowered his head. "One soul isn't meant to exist at two places at once. Due to my sons' souls' cycle of reincarnation, I couldn't displace them in time without risking to put them somewhere where they either already exist, or will be born too soon after. They are here too often for me to offer this opportunity to them. But you... You are something rare. Strong ninja born out of a civilian family. Your soul is entirely new. Made at your birth just for you, where most chakra users tend to be a reincarnation of someone from their own line. You, I only have to worry about sending far enough back to not interfere with your original birth."
Sakura thought on his words, glanced at the sky that was still darkening bit by bit, then nodded.
If she had a chance, even just a tiny one, to make sure the world didn't end like she had seen, she should grasp it with both hands.
"It is a good thing, too, that you still have a large reserve of yin chakra with you. It will help make sure that your memories make the trip with you." The Sage of Six Path said, making Sakura take notice.
Oh. So he was the voice she heard when she was about to use the last of her Strength of a Hundred seal.
He had made her hesitate in preparation for this last ditch measure.
Sakura nodded more decisively, and stepped closer to the old man.
A hand touched her forehead, right over the fading diamond of her seal, and she felt herself be sucked away.
Not truly up, down, forth back or sideways. Just elsewhere.
Ah.
She was... Not born.
At least that's what the blindness, floating sensation and the underdeveloped body her diagnostics detected told her
Of course.
Her own body had totally dissolved in the lava. There was no way the Sage could have sent anything but her consciousness back.
That was what the words had meant, then.
She was being retroactively reincarnated.
And the deep thundering boom that came from bones more than ears... That was her new mother's heart.
Huh.
It was actually pretty nice.
according to the chakra she felt, she was five to six months away from being born.
The wait might get tedious with time, but for the moment, it was just relaxing.
After everything she just lived through, all the upheaval and heartbreak and loss...
Yeah.
Five to six months of essentially sleeping in a nice, warm cocoon was pretty good.
An occasion to rest and recover.
Her eyes were closed. After all, she was a fetus. And there was no cover to tug over herself, nor air to yawn. She was already in fetal position too.
Well.
Apparently, she didn't need to move her body to make herself at ease before going to sleep.
She just dropped off.
There must be some link with how underdeveloped the brain she was hosted in was. Was her conclusion when she woke up again some undetermined amount of time later.
Most of her thought process must be supported by her yin chakra rather than her actual brain.
It was probably better to reduce her expenditure.
It wouldn't do to start losing memories from yin chakra depletion before she could even be born.
It wasn't like there was anything for her to do anyway. Nor any planning to do that she couldn't do better after her birth, once she knew who her new family was.
Right.
She reached for her yin seal, finding it less defined than she was used to. No matter. Her chakra control was the best.
She just needed to take all her yin chakra, push it inside the seal, and then force the seal closed.
She felt her consciousness fade to black as soon as the seal reluctantly closed.
Keeping the yin chakra in the seal was harder than it looked. With much less chakra than it needed to properly form, the seal was... leaky.
She could push all of her chakra inside of the seal and force it shut, but then her consciousness faded, and so did her conscious grip on the seal. So her chakra started to seep back out, until there was enough of it free for her to regain consciousness and force it shut once more.
In truth, that was convenient. The regular returns to consciousness allowed her to use a diagnostic and take stock of her body's development.
It wouldn't do to be in an unconscious period during her own birth and be pronounced stillborn.
She had also made the pertinent discovery that her new body was male.
That sent her for bit of a spin, but ultimately... Did she care?
She had been obsessed with looking feminine as a child. And okay, as a teen too. But she had been sent back in time to prevent the world from ending. Her sex was the least of her worries.
She wasn't a child anymore, and being ladylike or marrying Sasuke were no longer concerns.
After all, Sasuke was dead.
She knew that it wasn't the most healthy way to deal with it, but when those kind of thoughts came, she tended to take it as a sign to stuff all of her chakra back into it's seal.
Avoidance was a tried and true method of dealing with problems, shut up, Ino!
It was at the end of the second trimester, judging by the state of her lungs, that Sakura noticed it.
A small spark of chakra that wasn't hers nor her new mother's.
Sakura wasn't much of a sensor, but she had perfect chakra control within her body, and this almost transparent spark of chakra was definitely inside the same body as her.
Uh. Curious.
As if in answer to her interest, the small bit of... Baby chakra, started moving toward her.
She watched on entranced.
There, the chakra touched hers.
Then, the baby chakra changed.
As she observed that little flavorless spark of chakra, it started to turn into her own.
It was a tiny little amount of chakra, compared to hers, but still, she had perfect control, and she felt when the chakra started to belong to her.
She panicked.
It was only later that she understood why.
Once tucked into the seal, with just a crack open to let her keep thinking while still being separated from the body's brain.
That was yin chakra.
It hadn't been hers. At least not until it came in contact with her own chakra.
The small spark of featureless chakra. It was coming from the body's brain.
It hadn't emerged from the brain already being hers, it only became hers after meeting her own chakra.
So...
It was... The body's spirit.
Still weak and lacking consistence from being nothing more than a fetus. But still. A separate spirit.
The body she had been sent into... It already was meant to have an occupant.
Worse. She just almost squashed this native occupant.
If she hadn't taken the habit of stashing away all of 'her' into the seal most of the time, leaving the body mostly uncorrupted...
Chances were she wouldn't have even had the option of retreating into the seal quickly to preserve the body's spirit, because the brain would have progressed to the stage of being able to sustain a spirit with her already occupying it.
And then... This little soul would never have had a chance to bloom.
It wasn't even a real person yet, she knew that. But... Everyone had just died around her. She couldn't stomach to see another being cease to exist when she had the power to preserve it.
Especially this...
No. Her...
Twin?
Huh. Could she...
No. She couldn't produce a twin body for herself. It was much too late in this body's fetal development for it.
So.
Her baby brother.
She had a little brother.
She had wanted a little brother so much when she was still a child.
Now she had a literal baby brother. A little brother who needed her to not corrupt his brain with her chakra until his actual spirit was formed enough not to turn itself over to her at a single touch.
That was fine.
She had resolved to hibernate until she was born to conserve her chakra, and therefore her memories. No sense dwindling her supplies down when there was nothing active for her to do.
But if the Sage had sent her all the way back to the Warring Clans Era, then starting to plot a couple of years later wouldn't make that much difference.
She would need a fairly developed body to start influencing anything anyway.
All she needed to do was to be careful to shut all of her yin chakra into the seal, and to keep it firmly shut.
...
Except she still couldn't maintain the seal shut while she was unconscious and she couldn't stay conscious if the seal was shut.
She took another look at the body's chakra system, where the almost transparent yin chakra of not yet born baby was still flickering, but also still pure.
Well.
She could also simply put all of her yin chakra into the seal and then not shut it. It would let her stay conscious enough not to leak her chakra out while still partitioning her chakra from her baby brother's vulnerable brain.
She held onto that idea for... About five hours.
Then she understood just how boring it was to be a fully conscious, body-less yin chakra imprint inside of a not yet born fetus.
There was nothing for her to do. And even thinking about how wonderful it was to have a little brother didn't keep her that occupied.
And since she was no longer being physically hosted into a baby's body, she wasn't even that sleepy.
So she decided to experiment with exactly how small she could make the seal's opening without losing consciousness.
Which let her discover that if she let just the tiniest crack open, she entered a state of altered perception where she wasn't quite unconscious, but not quite conscious either.
Mindlessness.
With the seal open just enough not to lose consciousness, Sakura could drift mindlessly.
Just enough presence of mind to keep the seal a hair away from being shut.
After some time, counted in one or two days, her control would relax a bit, and she would be back to semi-lucid thoughts until she tightened the seal again.
But at least this method meant she never leaked her chakra into the brain and never corrupted her little brother's developing pathways.
About two months into her new routine, Sakura discovered an interesting side-effect of the mindless state she put herself into most of the time.
It seemed that while her consciousness was minimal, she still went through her memories and processed them.
Her grief was slowly losing it's edges as her semi-conscious mind turned it over.
She found herself thinking of Naruto, Sasuke, Tsunade-shishou, Kakashi-sensei or Ino in her clear-headed time, and not feeling the acute stabbing pain of immediate loss.
It still hurt, of course.
She had lost them all pretty much forever.
If she was lucky and didn't change any of the prerequisite moments, she might get to see Tsunade-shishou again, possibly Kakashi-sensei as a baby.
But still. Out of everyone she ever knew, she was the only one currently alive.
Except maybe for Katsuyu-sama.
And possibly Naruto's Biju, Kurama, but he hardly counted, Sakura didn't even know him from before her death.
Maybe the Tsuchikage or elder Chiyo of Suna?
Anyway.
Yes, she was all alone, and even having gained a baby brother with her reincarnation didn't change the breadth of her loss.
But her grieving process was at least made somewhat less painful by having large swathes of it happen unconsciously.
And she did have Baby Brother.
Someone who was hers, would always be with her. Someone to love forever.
Someone to save the world for.
After all, she knew that she tended to be passive if not for love. During her life, there had been plenty of things she should have done that she didn't do, and most of the things she ended up doing, she did because of Sasuke.
Saving the world for all of her precious people who would maybe be born a century in the future was very different to saving the world for her beloved little brother who was alive right now. She knew that.
Having someone she loved pretty much built in would also keep her from descending into apathy. How could she try and live in the past, mourning those who died, if she had a precious little life growing right in front of her eyes?
She decided to let Baby Brother handle the entire 'being born' business. Crawling out of her new mother during labor sounded exactly like the kind of experience she didn't want to have. Baby Brother had the advantage of very convenient infantile amnesia to deal with the ordeal.
She kept a thin string of medical chakra going, so she would know if anything went wrong with them or with their mom, but she stayed well tucked-in in the seal otherwise.
Being too mature to fake being a baby was one of the things she worried about before Baby Brother started to manifest. Sakura thankfully didn't need to worry about that anymore.
She could leave the entire 'being a baby' thing for her brother too. He was very well prepared to handle that by the virtue of being an actual baby. He could act as a baby way more convincingly than her.
Also, she was still wary of putting any of her yin chakra near Baby Brother's brain.
It was best to to let him grow up without disturbances. She still had a lot of grief to process, after all, she could keep minimal involvement until the body was at least a toddler and Baby Brother had an actual sense of self.
She decided the best time to start acclimating Baby Brother to her chakra and teach him not to try and absorb hers to be shortly before he turned two.
That was when she noticed that the native yin chakra stopped turning itself over to her the moment any 'Sakura-flavored chakra' touched it.
In exchange, Baby Brother had gained the worrying habit to try and eat her chakra any time she let it touch his.
It wouldn't worry her that much if the absorption was perfect. But whenever Baby Brother stole some chakra from her, it left behind a slight... coloration on Baby Brother's yin chakra.
And considering their differential in chakra reserves even without any physical brain for Sakura's yin chakra to regenerate, if she let this habit be, Baby Brother was at risk to cease being a distinct being to be slowly turned into a second version of her.
Also, she had stuff to do.
A world to save, all that.
One of the reasons why she decided to start taking care of that before the second birthday came around was because of infantile amnesia.
She didn't plan to hurt Baby Brother.
She would rather not, actually.
But the reaction seemed instinctual. And training instincts.... That didn't tend to work without some form of negative reinforcement.
The only alternative to the stick and carrot approach was to wait until Baby Brother was old enough to be reasoned with to teach him to restrain the gobbling up instinct.
And while she was still doing alright, the reserves of yin that she was anchored in were not bottomless.
She was going to need access to actual brainpower to start replenishing her chakra in five years at most.
Less than that if she had to use her chakra for healing.
So, while it may be a bit cowardly of her, she wanted to get the 'swat puppy on the nose with a newspaper when he misbehaves' thing done when Baby Brother wasn't likely to remember it later.
She wouldn't hide it.
She just didn't want that to be Baby Brother's first conscious impression of her.
Sakura started the process of acclimating Baby Brother to her yin chakra very slowly.
She extended very thin tendrils of her chakra into place where her Baby Brother's chakra was, and waited for it to react.
The moment Baby's chakra tried to absorb hers, she retracted the tendril as fast as she could.
If that way worked, she wouldn't have to resort to the stick.
It didn't.
In barely a week, Baby's chakra was trying to absorb hers even quicker in reaction to her fleeing any attempt to do so.
She really didn't like what she had to do next.
It was for Baby Brother's future safety and mental integrity.
But she still hated it.
The next time she extended a tendril and had Baby Brother try to consume it, she suddenly added chakra to the tendril in a burst and slapped out, before retracting.
Of course, after that, she ran a diagnostic to make sure she hadn't actually damaged Baby Brother's fresh and tender brain.
It at least succeeded in making Baby's chakra have a more cautious reaction to hers the next time she sneaked out a tendril, two days later.
Well.
The approach was more cautious.
The attempt to consume her chakra stayed.
So she swelled the chakra in the tendril up in warning, then retracted it.
It took a dozen of repeats, and three more little chakra tendril swats to make Baby Brother not immediately try to eat her chakra as soon as it came in proximity to his.
As a sort of reward for leaving her chakra alone, Sakura took to healing Baby Brother's sunburns and eye strain so long as he didn't try to consume the medical chakra.
Baby Brother had melanin deficiency. As in albinism. And he also had a thin skin that meant he got rashes from clothing and bedding.
Sakura tried to be discreet when healing either of those. It wouldn't do for Baby Brother to be labeled as possessing a new Kenkai Genkai. Too dangerous for him. So she always started with pain numbing, and worked the actual healing over a longer period.
And still, with her never doing the exercise more than twice a day, it took six months overall for Baby Brother to completely stop attempting to absorb her chakra into his.
Thankfully, over the last three months, she hadn't needed to resort to slaps at all, and just a warning swell was enough to get him to stop.
With the risk of her chakra polluting Baby Brother mitigated, it was time to turn her attention outward.
Which in this case, meant connecting herself to the different sensory centers in the Body's brain to be able to perceive what was happening.
So far, she had only been vaguely aware of what their environment was like by tracking the Body's condition with medical chakra.
For instance, she knew that Baby Brother had been given real knives at twenty-six months old due to the cuts on their hands.
She was furious at that particular detail, but she reminded herself that it was the Warring Clans Era, and some Clans out there made a sport out of killing actual babies. Knowing how to defend yourself from a young age was necessary for survival.
After getting tendrils into the different sensory cortexes and about a month of working out how to interpret the input into something understandable, she settled in to observe.
It took Sakura an embarrassingly long time to learn the name that their parent had chosen for Baby Brother.
In her defense their mother and brother tended to call him Tobi-chan.
And yes, alright, mom called their 'older' brother Hashi-chan.
She just didn't note it until their father called him Tobirama.
Tobirama.
Baby brother was Senju Tobirama.
She had almost caused the Second Hokage not to exist.
That sent her in quite the mental tailspin.
How could the Sage of Six Paths have stuffed her inside of the Nidaime when causing him not to exist was a much more likely outcome than the current coexistence?
Well.
Yes, alright, Konoha would be pretty much doomed without Tobirama.
He was the one who made the policies, laws, and most of the blueprints for amenities and sewers.
Good news was, she didn't actually cause Tobirama to not exist.
So... It was fine, right?
She could keep Baby Brother from making the Uchiha into Konoha Military Police or teaching Danzo, and make the Uchiha massacre not happen, and everything would be fine.
So.
In the past, Uchiha hadn't been massacred yet.
And they were in a bloody feud with the Senju.
Her new Clan.
And their new father had already started making it known to them that he didn't think sons had any value unless they could kill Uchiha.
In the middle of making little Tobirama train. With live blades. At two years old.
Sakura had heard it because she ran a tiny amount of medical chakra in their body at all time so she could intervene when Tobirama got hurt. She had noticed a cut on their arm and had threaded chakra into their sensory centers to find out what was happening.
Only to hear their father scold Baby Brother for not being a perfect shinobi and failing to stop a slash.
As a toddler.
Tobirama was even on the young side of toddlers, since he learned to stand very young.
She kind of hated her new father.
Okay, no. There was no kind of. Sakura hated her new father.
Hmm.
She would have to see about him having a 'heart attack' when Hashirama was old enough to handle the Senju headship.
For now... Hah.
Hashirama was barely four. And their mother was pregnant with the third out of four Senju heirs (she remembered four from the Academy's history lessons, at least).
She unfortunately needed that asshole still.
The Senju might have been painted as the good guys in Konohan propaganda, but Tsunade had told her otherwise. If their father died before Hashirama could take up the responsibilities... Or at least before he awakened his Mokuton... There were chances that whoever got 'temporarily' appointed as head would get rid of Butsuma's children to be able to keep power for themselves.
Power, especially Political Power, was just like that.
Very few people could handle it without getting corrupted by it.
That was one of the many reason why Sakura's Shishou was so banging awesome.
Well... Had been so banging awesome.
...
Would be so banging awesome?
Hmm.
For the moment, she numbed the pain from the cut and slowly threaded healing chakra into the wound. She definitely didn't want Tobi-chan to be noticed for an abnormal healing capacity. But speeding up the scabbing a bit and ensuring no infection set in was still safe.
Especially since 'father' had dismissed them after his scolding.
Even if mother noticed, she wasn't going to tattle.
Hopefully.
Baby Itama was the cutest newborn she had ever seen.
And she had seen a few of those, working in the hospital.
They usually were kind of ugly.
But.
Okay, so baby Itama was also kind of squashed.
But she totally got why Tobirama-chan wouldn't stop staring at his new brother.
Itama-chan was just too cute.
When the little two-colored infant grasped Tobirama's offered finger and then stuffed it in his mouth, Sakura felt something settle.
Ah right. This was it.
She was meant to be an older sister.
It had to be.
That was her calling.
She was an older sister.
She would protect these precious babies.
It wasn't like the adults nominally in charge were willing to do it.
So that was her new form.
A new way of life for her new life without everyone she knew before dying.
She was an older sister. She had three adorable little brothers. (Yes, Hashirama was also a little brother. He might be Tobi-chan's older sibling, but Sakura was oldest.) There would be a fourth one shortly if things kept progressing as they had in the historical records of Sakura's life.
She would care for them.
No one could stop her.
She was Tsunade-shishou's apprentice. No one in this era was even remotely prepared to handle her.
So what if she was a mostly bodiless chunk of chakra at the moment?
That was temporary.
She had studied how Inner manifested in her brain on a physical level out of idle curiosity. She was uniquely qualified to handle creating a space within their body's brain to ease cohabitation. It simply needed a tiny bit more time for Tobirama's yin chakra to start solidifying before it was safe to attempt.
She was sure Tobi-chan wouldn't mind.
After all, she could read his devotion in the waves of his yin chakra. He was just as invested in his siblings as she was.
She never knew Tobirama-sama, the Nidaime Hokage before dying, but Tsunade-shishou sometimes spoke of him. A gentle if stern-looking uncle, doting and kind. Intelligent, ingenuous and curious of everything.
If Tobi-chan grew up anything like that, he would surely welcome her as a valuable resource in protecting his beloved brothers. And possibly an intellectual curiosity to try and comprehend.
And... She had a feeling that Tobi-chan already knew that she existed.
Not in any detailed terms, of course. But Baby Brother was smart, even at his young age. A little genius. And also a natural sensor.
The more time passed, and the more she could feel Tobi-chan chakra react to hers when she sent it into his body, be it to heal or to watch their surroundings. Depending on how much chakra she channeled in, his would either move away to give hers space, or twin around hers curiously.
She had noticed that Tobi would start relaxing his muscles before she even got around to numbing pain as soon as she started channeling healing chakra through the body's pathways. A tiny timing difference, but enough to tell her that he recognized something. Even if only unconsciously.
And Tobaby was only Thirty-two months old.
She wasn't sure why it was Hashirama-sama who got called God of Shinobi. Tobirama was incredible. She wasn't even being all that biased! Hashi-chan was also her cute little brother. Tobi-chan was just a genius.
When their body was three, Sakura deemed Tobirama's brain stabilized enough to start very carefully creating a system so she could use their body's brain resources to generate her own chakra.
She mostly worked on it during the night, because doing so when Tobi was awake caused him to get distracted from his daily life activities. And their father was an asshole who would punish a literal baby for wandering attention.
The first order of business was to create a stable link from the seal (that still was in the middle of the forehead, despite not being outwardly visible yet) and the sensory centers, so the yin chakra, and linked consciousness, stored inside the seal could see what was happening to the body all the time without any complicated operations.
After all, she was probably going to need to assume control at some point. The best way to command the body without it being overly complicated would be to tuck all of Tobi-chan's yin chakra in the seal and place hers in the brain instead. Then she would be able to move things naturally.
But she didn't want to end up locking Baby Brother in sensory deprivation.
She had to experiment a bit until she managed to create a stable double to the sensory center, but she managed within a few weeks. Putting the linking channel between the two hemispheres of the brain to avoid interfering with Tobi-chan's native chakra ended up being the best way to manage that.
Over the following month, she used diagnostics jutsus a lot to see which parts of the brains were the least used so that she could implant her own chakra there and start actually having brainpower to allow her to create more yin chakra.
It took her even more time to devise a way to safely herd her baby brother's native chakra away and create solid borders so her consciousness wouldn't leak out and contaminate Tobi's sense of self, before she could actually put her own chakra in these select spot and... Well, sort of start parasiting their body's brain.
While she would like to respect Tobirama's bodily autonomy, she wasn't willing to let history repeat. She had to intervene and change things.
And to do so, she would need enough yin chakra to be able to think, and, at one point or another, an actual body to do stuff in. Which would end up being the body that was originally meant to be Tobirama's. Simply because she had access to no other body.
Taking less used parts of his brains didn't make her happy, but it was the least harmful way she had to get the two of them to a desirable outcome.
She was going to need to be more and more active as time passed, and her chakra reserves were depleting frighteningly fast.
At last, about when Tobirama was three and a half, she had a solid link both to her Baby Brother's bodily perception and to some minimal brainpower that allowed her to break even on chakra production and consumption.
She still made sure to put the most active times of using the brain to think and produce yin chakra when Tobi-chan was asleep, but overall, Baby Brother seemed to have gotten used to her presence quite well, and he rarely startled or zoned out anymore when she did things.
On another subject, Sakura was getting pretty worried about their mother. She was pregnant enough to start showing, and while Tobi-chan was mostly overjoyed to be getting a new sibling, Sakura's medic side was calculating the gap between pregnancies and disliking the results she got.
The newest baby had been conceived mere months after Itama-chan's birth.
It wasn't quite back-to-back, but it was way too close to allow their mother's body enough time to properly recover from her previous child.
And their mother was also minding all three of them, trying to reign in Hashirama's enthusiasm so he wouldn't get punished by their father, minding Tobirama's delicate skin, and taking care of baby Itama.
She was looking sleep-deprived.
And there wasn't much Sakura could do to help.
Tobi-chan was already being as much of a little angel as possible and taking up Itama's care whenever he could.
As months slowly passed, Sakura noticed that the quality of the new yin chakra made from her co-opted bit of brain was pretty childish.
At first, she simply made sure to use that part first, but after a while, she started wondering if it was possible to make her brain portion age up a bit with medical jutsu.
She was extremely cautious about that. She went slow and checked her results over meticulously and waited to see if there were any unwanted effects before doing anything more. She definitely didn't want to create a brain tumor.
But over a couple of months, she managed to get her little bit of brain evolved enough that she was creating more chakra than she was consuming.
Sakura wasn't surprised when their newest brother was brought to them by a young woman with a slightly older baby strapped to her chest. She awkwardly introduced herself as their little brother's wet nurse.
Tobi-chan didn't immediately understand. But if he would grow up to be able to sense all the way to the Fire country border from Konoha, he was perfectly capable of sensing his mother in the same house as him at four.
Sakura didn't get information such as sensing from her link with Tobirama. Probably because it was information that came from chakra rather than nerves.
But she definitely saw Tobi-chan sneak away from supervision and head to a room to the back of the great clan-head house.
Sakura had no trouble recognizing the smell of a terminal patient.
When Baby Brother crept close and took his mother's hand in his, calling her, the woman turned her face toward him.
Her skin was too pale from blood loss, but with big red blotches that spoke of a high fever. Her eyes, when they turned to her son, were glassy and stayed a bit unfocused even after she recognized him.
She had very little time left to live.
She was probably in a lot of pain, too.
But still, she found the strength to squeeze Tobi-chan's hand and smile for him.
And then she spoke. "Tobi-chan. My Tobirama. I love you. I love you all so much. Please. Take care of your brothers for kaa-chan."
"I will. I will kaa-chan, so..." Tobirama didn't get to finish his plea. Their mother smiled happily and gave a relieved sigh. Then she closed her eyes and went still.
Sakura wasn't a very good sensor. But she was good enough to sense someone dying at such a close range.
Tobirama... His sensing was much better that hers. Sakura was worried how detailed his perception of his beloved mother's death could be.
For a moment, Sakura absolutely hated that woman.
How could she be so cruel as to hold on only long enough to die in front of her child? She wanted to make sure to tell her children not to hate the youngest for her death, Sakura could respect that. But couldn't she have waited to give up on life until Tobirama wasn't holding her hand?
She saw Tobi-chan touch his mother's cheek in confusion, then the death must finally have registered to him, because he let go of his mother's hand in a panic and rocked back. Then he lunged forth and grabbed onto the bed-covers, yelling into them for his mother.
Sakura couldn't do anything to help him. Even if she had been willing to expose her presence and her talents, she wouldn't have had enough chakra to heal the kind of injuries mother had. Complicated births got messy, even with modern medicine.
And Tobirama was, among other things, the inventor of modern iryou-ninjutsu.
The medics of this time hadn't been able to help on the spot, and by the time Tobi found his mother, infection had already set in.
Actually, there was a good chance that this exact moment was why Tobirama-sama ended up deciding to invent modern medical jutsu.
Tobi-chan's cries must have been heard, because the sound of hurried footsteps reached their ears.
Sakura thought for a moment.
By the time the door flew open she had made up her mind.
Baby Brother was in a lot of pain, and he would not react rationally to being removed from the room.
It was a simple matter to put a small jolt of chakra in the right nerve cluster and cause Tobirama to fall unconscious.
Her diagnostic jutsu didn't detect any new bruise from falling down, so she assumed that someone had caught Tobi-chan before he fell to the ground.
Sakura had a temper.
She had always had a temper.
And seeing Senju Butsuma slap Tobirama-chan for crying at his mother funeral before turning toward Hashirama to do the same... That ignited her temper.
She snapped.
The time it took to carefully collect all of Tobi-chan's chakra and tuck it away into her yin seal, then monitoring the spread of her yin chakra into the brain to make sure it didn't sink in too far meant that she only took control of the body after Hashi-chan got slapped.
But once she had control of the body...
Butsuma's arm snapped in her grip. Sakura snarled and kept twisting it viciously.
The Senju Clan head grunted and tried to hit her with his other arm.
The hands at Sakura's disposal were fucking tiny, and she had very little chances of managing to grasp her 'father's' arm while it was moving. So she just swatted the hit aside.
Even after years not using it, Tsunade-shishou's strength enhancement came to her easily. An audible crack signaled Butsuma's other arm breaking.
She let go and jumped back, keeping her teeth bared in anger.
The man who Tobirama would have called father but who was no such thing to Sakura glared at her, both arms hanging by his sides. "Who are you? What did you do to my son?" He spat her way.
The wind caused a lock of slightly ashy pink hair to say into her field of vision.
Sakura blinked and curiously caught the lock of hair.
It wasn't quite the same shade as hers had been. A bit washed out, a bit grayer. But still pink.
It also had changed texture. Where Tobirama's hair stood out in grayish spikes, it was now falling around her face like hers had used to.
Apparently, letting her chakra flood the body caused some physical change that brought it a bit closer to her original appearance. Not that she could catalog them at the moment. She had something to do.
She straightened with all of the body's tiny, four year old height.
Her eyes traveled around her. Her brothers. Six years old Hashirama, holding his cheek and goggling at her. Little toddling Itama, not able to understand what was happening. Infant Kawarama fussing in his wet nurse's arms.
"You can call me Sakurama." An added syllable to make her match her little brothers' naming scheme. "For better or for worse, I am Tobirama's twin. And if you ever hurt my brothers again, I will make you pay dearly for it."