Healing
Due to her harsh upbringing, Hinata was a shy and uncertain girl. However, there was a light in her life, someone who inspired and motivated her to move forward – Naruto. She watched him being knocked down again and again, but he would just get back up and push forward. She could never master the courage to approach him, always saying "next time".
At first, she hoped to get on the same Genin team with him. Then, she fantasized about doing join team missions or training with his team. However, as one opportunity passed by another, she started to realize that they were drifting apart, rather than getting closer together. They saw each other less and less, and that just couldn't stand.
When Kurenai announced that she nominated their team to the Chunin Exams, Hinata has only one question "Were other rookies going to participate as well?". Even though she didn't think she was ready to be Chunin or even to participate in the exams, she saw this as her last opportunity to catch Naruto's attention.
The exams turned out even more brutal than she expected.
For the written portion, she used her Byakugan to ensure she sat next to Naruto. When she realized he didn't know how to answer any of the questions, she gathered all of her courage and offered him to cheat off her. While he declined, it definitely caught his attention, which made Hinata float for the rest of the exam.
Forest of Death was brutal. There was death and misery anywhere she looked, and the good portion of the forest was within her range. There were few close calls, but being tracking specialist team, they had it easier than most.
Then came preliminaries. Even while fighting the worst possible opponent, her cousin Neji, she managed to get Naruto to cheer for her! She was just so happy, even the pain and numerous Juken strikes couldn't keep her down. She made sure to watch Naruto as she announced their shared Nindo, if that didn't catch his attention, then she didn't know what will.
It was days later that she learned of the price she paid. Doctors spend 10 hours trying to keep her alive after the match. Her heart stopped 3 times during that time, longest being full 7 minutes. Even now, days later, she was still exceptionally weak. Doctors gave her very strict orders of no training or chakra use, of any kind, until she fully healed.
Even for the Finals, month later, she was still on strict medical leave. That didn't stop her from finding Naruto just before his match. She gave him the encouragements he needed, and confirmed that her efforts were not in vain. She could proudly say that they shared a connection now, she just had to work on strengthening and expanding it.
Then came Sound and Sand Invasion. She missed most of it due to having another cardiac arrest, that was triggered by her attempt to use a small amount of her chakra. The doctors were at a loss what caused it. She was not fully healed yet, but she should have been out of danger zone by now.
It took a few detailed examinations by the Fifth Hokage – Tsunade Senju, who happened to be worlds renowned healer, to determine the cause. When Neji hit her with a Juken to the heart, he also hit her Chakra core.
Normally, it would not be an issue, and her core would have eliminated or pushed out the foreign chakra over time. However, his chakra was significantly stronger than hers, and he pushed quite a bit of it into her core. This meant, that her core wasn't strong enough to fight it off. Instead, any chakra she produced was assaulted and absorbed by Neji's, only strengthening it and making it harder to eliminate.
"Frankly, Hinata, I am amazed you are still alive" was the Hokage's diagnosis. The running theory was that her chakra exhaustion and near-death experience saved her. It kept Neji's chakra long enough without target to attack, that it reversed back into its natural, unmolded, calm state. In this state, it was no longer actively trying to kill her, but introducing any other chakra in its vicinity, like her own, caused a violent reaction.
"I will keep looking into possible solution, but I want to be honest with you. Your ninja carrier is likely over. Even getting a bruise may kill you, as your body will naturally generate chakra to speed up the recovery, triggering another cardiac event."
Her father didn't waste time in announcing Hanabi as the new heir. At least, he had decency of asking Tsunade if Cage Birded Seal can be applied to Hinata. If he didn't, it would have most definitely killed her, by constantly drawing on her chakra.
Neji avoided her like plague, whatever due to guilt, or something else, she didn't know. The only time she even saw him, was after his failed Sasuke retrieval mission, where he was hurt badly and was bedridden. Even then, he was always 'asleep' when she visited.
One good thing that came up from her injury, was that Hanabi, her little sister, become a lot warmer and kinder to her. Hanabi visited her at least once a day in hospital, and made point of always stopping by her room once she got released.
Even though she was no longer part of the Team 8, they continue to meet and support her. If they were not on a mission, they went for a lunch once a week. Her place on the team remained unfilled, only being filled by random Genin during missions. She thought they kept it open for her, and was very touched by it, but no one said anything. Her team was the best!
Naruto left for the 3-year training trip shortly after failed Sasuke retrieval mission. He was hurt pretty bad, so Hinata made a point of visiting him in the hospital, and they had a few short, but pleasant discussions. He didn't know how bad her injury was, she couldn't bring herself to tell him about it. There was no point of him worrying over it.
Hinata never really gave up on the idea of being ninja. She was just starting becoming friends with Naruto, and she was not going to let it go, no matter what. Then there was The Nindo she adopted.
(*H*)
One year, and 15 cardiac arrests later, she thought she finally found a solution. It came to her while watching Shino train. His Kikaichu bugs were very weak individually, but together, they were nearly unstoppable. She just needed to do it in reverse. Rather than trying to fight Neji's chakra as one big blob within her core, she should split it into smaller blobs and then take care of each one individually.
It took her another month and 3 more cardiac arrests before she was able to push a single, minuscule blob of Neji's chakra out of her core and into her chakra network. Then, she simply pushed it out of the nearest Tenketsu point.
A week later, she had managed to get rid of 3 more blobs. This is when she realized, that while she was making some progress, for the first time since injury, it was very slow going. She would be older than Tsunade, by the time all of Neji's chakra was pushed out this way. It simply took too much time to generate enough chakra to push foreign chakra from her core. It felt much like pushing a log upstream of mountain river.
This was another piece of puzzle, but not a solution on its own. She now had 3 different pieces, so she had to find 4th, perhaps, it will lead to the final solution. So far, she learned how to generate chakra in precise place in her core, away from Neji's, so she could move it out of the core before it got absorbed, but only in small quantities. Then, she learned how to move Neji's chakra within her core, by using some of her own chakra as bait. Now, by using multiple baits at the same time, and very precise maneuvering within her core, she learned to split Neji's chakra into smaller blobs, that were much easier to handle.
Over the next few weeks, Hinata had her sister inject small portions of chakra into her network. Hanabi was 5 years younger than Hinata, so even now, Hinata's chakra was stronger than her sister's. Additionally, the injections were outside of the core, so there was very little risk involved. This allowed Hinata to do a lot of experimenting, pretending that her chakra was Neji's and Hanabi's was her own.
Over the course of her injury, and the time of experimenting, Hinata had learned quite a lot about chakra, as well as developed a very accurate chakra sensing ability. As far as she could tell, there were 3 properties to the chakra: Density, Charge and Volume.
Density, as far as she could tell, was direct indicator of ninja's chakra strength. It grew as ninja trained. Even over the short few weeks of working with Hanabi's chakra, she could see noticeable changes in its density.
Charge, on the other hand, seems to point to the state the ninja was in. While well rested, the chakra was much more energetic than when ninja was exhausted, after hard training session.
Volume, was the amount of chakra present, the size of the blob.
The less dense and energetic chakra was, the more of it was needed to complete a Jutsu of the same strength. From what she remembered of her Byakugan use in the past, it could only perceive Volume of chakra, but not the Density or Charge. This explained to Hinata a lot about Naruto. She always questioned why he was able to create so many Shadow Clones. His reserves were just above that of the Third Hokage, and his chakra control nearly nonexistent. In all likelihood, his chakra was scarily dense, since charge was not something that could be consciously changed, as far as she knew.
Interestingly, when stronger chakra absorbed weaker one, the Volume and Density were not affected, but the Charge was. Hinata was able to supercharge her own chakra with Hanabi's, but even that wasn't enough to defeat Neji's. She theorized, that if difference in Density was too big, then the stronger chakra couldn't be defeated, no matter the Volume or Charge.
Keeping that in mind, Hinata went through her whole clan collecting small injections of chakras from numerous children, looking for the chakras with different densities between her own and Neji's.
It took another few weeks, but she finally figured out path to recovery. When densities of chakras were close enough, then weaker one still could win over the denser one, but it required to have greater Charge or greater Volume. For her own chakra to beat Neji's, she had to use chakras of 12 others in her clan to bridge the gap between their Densities.
To say that process was tedious and complex is to say nothing. There was no way to make the transformation in a single batch, the Volume of Neji's chakra in her core was too great, there was no way she could get rid of it all at once. She had to do it in small batches, as any big conflict within her core would cause her another cardiac event, and The Fifth said that she wouldn't be able to take too many more of those.
Then, she couldn't keep asking people to inject their chakra into her. There were already a lot of rumors going on about her masochistic and suicidal tendencies, from all of her healing attempts and hospitalizations. Tsunade wasn't particularly happy to discover paths around her heart made by Shino's Kikaichus. It was an attempt to get as close as possible to her core, so his bugs could suck Neji's chakra out of it.
Additionally, all of the chakra donors were still growing, and density of their chakra was ever changing. Hinata couldn't afford to have to constantly adjust the procedure and look for new donors. While she was happy for Neji's chakra to be absorbed in full, she had to figure out how to keep the donors chakra intact until the very end.
It took a few more weeks, but she learned how to separate the foreign chakras that were in the process of ducking it out, by pushing a wedge between them with her own chakra. It, inevitably, resulted in some of her chakra being absorbed by the both foreign chakras, but it was worth it to keep the original donor's chakra alive.
In essence, she had to keep 13 different foreign chakras within her core separate from each other and from her own chakra, despite their natural tendency to try to merge into all out fight. Then, she had to separate a precise amount of Neji's chakra from the main blob. Juice up next strongest foreign chakra blob with her own chakra, so it was capable of absorbing Neji's, then let them meet. Juice up next in line blob, make them meet, but break up the interaction in very precise moment, when the stronger blob was mostly exhausted. Rinse and repeat 12 more times.
By the time it was time for her own chakra to absorb the charge from the weakest donor chakra, it was positively glowing from all of the absorbed Charge on the way. Its Charge was easily greater than hundred times the normal amount.
(*H*)
Nearly 2 years later, with very little sleep, but with exceptional chakra control, Hinata was able to eliminate the last of Neji's chakra from her core. What was curious, that by the time the process was done, she had already eliminated the 3 weakest donor chakras from her core. For unknown to her reasons, the density of her own chakra started to grow as soon as she started to assimilate Neji's. She never noticed the effect when she practiced the procedure withing her chakra network. It seems, that when the foreign chakra was assimilated within her core, it got strengthened somehow.
The first person to know about her recovery, was Hanabi. Hinata surprised her by activating Byakugan for the first time in 3 years. It was like meeting a dear friend after a long separation. It was unexpected, how much she missed the view of the world through her Dojutsu.
"Hell yeah! Watch out the world! Team 8 is back together!" was Kiba's enthusiastic reaction, followed by the rare team hug. Hinata could only give her old team a sad smile.
"I wish Kiba-kun, but both you and Shino-kun are already Chunin, and well on your way to Jonin. You need to realize, that in the last 3 years I did zero amount of training. Right now, I am even weaker than I was when we participated in the Chunin exams, all those years ago."
"It doesn't matter. Why? Because we will help you to catch up" was Shino's contribution.
"I would really love that, but I don't want to hold you back" as she saw them trying to object, she raised her hand to finish "Perhaps you will not see it that way, but I will" at their dejected looks she added "Perhaps we can meet an hour before our usual lunch meeting once a week? We can train together, and you guys can give me some pointers?" she suggested a compromise.
"Two hours!" said Kiba with stern gaze, she looked at the rest of the team before nodding in defeat.
"How did you manage to overcome the injury? If you don't mind me asking" asked Kurenai
Hinata thought how to best answer that, she had no reservations about her team, she trusted them all completely.
"Do you know about chakra density?" she asked the team, getting blank looks from them, except Shino, who looked surprised.
"It seems only Shino-kun knows. While trying to find solution to my injury, I studied chakra in very fine details. There are 3 properties to chakra that I discovered: Density, Charge and Volume" she began explaining.
"3?" asked a little confused Shino. It seems even his clan only knew about two.
"Hmm, imagine chakra is a shinobi" getting understanding nods, she continued "Density is how strong the shinobi is. Charge, is the state of the shinobi, whatever he is well rested, or exhausted, or injured, or used soldier pills, etc. Does it make sense" she could see the team thinking hard on it.
"And Volume is how much chakra the shinobi has?" asked slightly confused Kiba.
"Not quite, how much chakra the shinobi has in rested state is part of Density, but how much chakra he has at this moment is part of Charge?" she tried to explain. "You can think of the Volume as in how many shinobi's there are" getting hesitant nods from the team she continued.
"Basically, my problem was that density of Neji-nee-san's chakra was much higher than mine. In essence, when my chakra tried to expel his, it was like throwing Genins to defeat a big group of Jonins. No matter how many of them I threw, they were all defeated" she explained, getting looks of understanding from her team.
"So how did you manage to defeat the group of Jonins?" asked intrigued Kiba.
"In essence, I hired other Jonins to do that. They were slightly weaker, but I gave them all chakra pills to compensate. Then I got another group of Jonins, even weaker to take on the last one, and so on, until there were only other Genin's left that my own could defeat" she explained.
"Did you speak with Tsunade-sama about re-registering? Do you want me to come with you?" asked Kurenai.
"I thought about it, but as I mentioned, I am in no shape to return to active duty. I would like to take some time to do some training first. Also, I am trying to keep my recovery a low profile for the time being. Wouldn't want my father stamping the clan seal on my head, before I got some time to get used to the idea" she explained to her team.