In a war where a single man, who was injured, could return to continue causing destruction, it was vitally important to deal with the medical ninjas who could return that ninja to his previous state.
And even if they are very well protected by their villages, doctors will never be 100% safe.
Knowing that he would be involved in the war because of his status as Tsunade's disciple, Natsuo thought about his chances of survival and how he could increase them when he realized that he would only be 11, 12, or 13 years old when the second ninja world war began.
Despite training every day and having an amount of chakra comparable to that of an elite jounin, approaching that of a jonin, it was not enough to be completely sure of not dying in future battles.
Although a ninja grew faster than normal due to chakra, Natsuo would only be a child entering adolescence during the war and his body would not have fully developed.
Thinking about this, Natsuo suddenly decided to increase his growth rate.
Of course, it was dangerous to simply stimulate the pituitary gland like that, so he returned to his experiments on mice.
Seeing that there was nothing unusual so far with these 2 mice that he artificially raised 2 months ago, Natsuo will wait another month before releasing them into the forest and experimenting again with another 2 mice.
Since he was not in a hurry, he waited to perform a few more accelerated growth experiments on several mice before thinking about using the same procedure on himself.
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The days passed and Natsuo continued with his daily life.
He would get up early in the mornings to train physically and then decide whether or not to go to the academy.
If he didn't go to the academy, he stayed at the orphanage to do his ninja training, such as throwing kunai and shurikens.
In addition to that, Natsuo now began practicing elemental chakra transformation in the mornings as well.
Each person had one or more elemental affinities that made it easier for them to learn and launch jutsus of those elements.
Of course, you could also learn and launch jutsus of other elements, but it would be more difficult and you would spend more chakra than normal.
Natsuo had not yet tested his elemental affinity because he already had his plate full with his training and experiments.
But since the Accelerated Growth Project would take a long time to be sure of not leaving negative consequences, Natsuo could spend his time practicing his elemental affinity.
Or elemental affinities in Natsuo's case.
In addition to the fire element typical of the Uchiha, Natsuo also had an affinity for the wind element.
The chakra paper he used showed a few small cuts, but everything else quickly turned to ash, showing a greater affinity for the fire element.
Natsuo thought about it for a few seconds before deciding to train the fire element first.
As much as he wanted to learn how to quickly throw a Rasen shuriken, Natsuo knew it would take a long time and it was better to train his affinity for the fire element first.
Furthermore, this reminded him that he had to learn the Rasengan, so he practiced it during his training as well.
In addition to his training or attendance at the academy in the mornings, Natsuo went to the hospital in the afternoons to learn from Tsunade.
And at night, he spent the hours before sleeping practicing his chakra control and also returned to practicing his elemental affinity for the fire element.
Natsuo was very busy with his current training, but the shadow clone jutsu came to the rescue.
While attending the academy, he would leave a shadow clone in his room practicing transforming his chakra into the fire element, and when it dissipated when he ran out of chakra, the clone's memories would be stored in Natsuo's mind palace until he decided he had time to absorb them.
In that way, he also spent a large amount of chakra when he went to the academy and didn't have to control the amount of chakra that escaped from his tenketsu.
Because he had great chakra control, he could create 2 clones with enough chakra for his training, so Natsuo suddenly felt like he had more free time.
Thinking of some way to occupy his time, Natsuo suddenly remembered the technique of the 8 inner gates.
In a ninja's body, there were 8 chakra points that limit a person's chakra flow.
That prevents someone from exerting their full potential strength, but it's necessary because otherwise you'll die.
Although he had memories of his past life, Natsuo wanted to go to the hospital library first and look for any mention of the 8 inner gates.
Until now, Natsuo had only read mentions of these doors in a few books and hadn't yet found any safe ways to open them. And for the next few days, he focused on finding precisely that.
Unfortunately for Natsuo, he found nothing that would help him.
Of course, Natsuo reasoned that due to the danger of manipulating these 8 internal gates within the body, he couldn't find them in a library where just anyone could find them.
And he confirmed it when he asked Tsunade and she told him that so far no one has managed to safely open these doors.
According to Tsunade, opening any 7 of the 8 inner doors places a great strain on the body.
And since very few ninjas focus on physical training, no one has studied these inner doors.
From what little he was able to glean from Tsunade, Natsuo realized that they didn't know the correct order to open these doors.
The only thing they know so far is that they must not open the chakra point in the heart or the ninja will surely die.
With a smile, Natsuo didn't mention that someone like that would appear in a few years and returned to his room and lay down on his bed before entering his mind palace.
In his mind palace, he focused on his memories of the program in his past life and found his memories about the inner doors.
The first two doors were those of the brain.
The third and fourth were located in the spinal cord.
The fifth one was located in the abdomen.
The sixth and seventh were located in the stomach, and the eighth and final door was that of the heart.
With renewed motivation, during the following days Natsuo focused on his physical training while keeping an eye on the 2 internal doors in his brain.
Since he knew that the first door was located on the left side of the brain, he focused on that side of the brain during his physical training.
And each day, Natsuo pushed his body further and further to the limit until months after starting his third year at the academy, Natsuo managed to open the first inner door.
Because Natsuo had great chakra control, he was able to stimulate the first inner gate very slightly and delicately, and it only took him 1 month of constant training where he always pushed his body to the limit.
And because he could heal his body, he was always as good as new the next day, ready to train again.
Clenching and gently releasing his fists, Natsuo could feel the power he could now unleash.
Sensing the inside of his body, he could feel the pressure his body was experiencing and calculated that he could maintain this state for one minute before having to deactivate the technique.
Thinking about that, Natsuo focused on the first inner gate in his brain and tried to control the flow of chakra.
And in just a few seconds, Natsuo returned to his previous state.
Sensing his body now, Natsuo winced in pain and quickly felt the damaged areas on his body before using medical chakra to heal himself.
In less than 2 minutes, Natsuo nodded his head in satisfaction at not finding any negative consequences on his body.
But that wasn't all.
As with any recovery after injury, Natsuo could feel that his body was a little stronger than before.
The increase was minimal, but Natsuo's senses about his body were amazing and he could feel the difference.
Thinking about this, Natsuo realized he could use this to take his physical training to a new level.
With a smile, Natsuo added opening the first inner door to his training routine at least once a day.
And when he felt his body could increase the load, he planned to open the first door 2, 3 or more times a day and heal his body after each opening.
Natsuo sighed in relief because he was able to find a way to become stronger quickly.
As long as he uses his new physical training method every day for the next few years, Natsuo will have a much better chance of surviving in the coming years.