Chapter 1: A terrifying world

Mc: A former medico reincarnated in Naruto anime. His appearance is the same as his profile pic.

AI in BOLD or [ ]

Authors note: * IMPORTANT* The Hypotheses are for those wanting to immerse in the world-building. Readers who want to progress with the story can skip them.

ATP is just the smallest form of calories. Like cells are the smallest unit of our body. So, think about ATP= physical energy.

P.S. - The first chapter more or less explains the mechanics of Chakra, so don't worry about that all the chapters will be so into heavy.

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'80…81…82…'

Even after a month of living in the orphanage, I still feel the pain of losing my family and being separated from them in this world as well.

'83…84…85'

I lost them twice: once by being reborn here and again by the second Ninja war. The mementoes given to me show their exact appearance from my previous life.

In this life, Dad was a merchant based in Konoha, who got killed along with Mom when he went to visit his native village. It happened when the Jonin team assigned to him went to support a returning Anbu team. Now the Anbu might be rescued, but a robbery gone wrong in the village resulted in the death of my parents.

Well, they demoted the Jonin, and they gave a mark to the Genin. Konoha slaughtered the bandits near my dad's village, but the result is an orphan, me.

At least, they arranged me in the topmost orphanage in Konoha, which was well-funded by donations. Perhaps it was a hidden sorry from Konoha.

They sold my parents' properties in the village and put the money, along with the 'sorry' money, in an account for me to claim when I become an adult.

By village, I mean the one where Dad was born. Konoha is not a village anymore, but a city by feudal standards.

'86…87…88'

So, my second life is a mess with me being an orphaned civilian, but the sad part is, I don't have chakra now. The key word is "now."

'95…96…97'

According to the storybooks in the orphanage, the sage gave chakra to everyone. I can understand it as the fact that sage of six paths remade the DNA of a significant proportion of the population to mould chakra. How he did that was a mystery to me.

Over centuries, the first chakra users' DNA reached everyone in subsequent generations.

The '98…99…100'

"Fucking finally!"

With my face pressed into the grass, I kept breathing hard from the exhaustion of doing 100 punches.

"One set down."

Now, as I was saying, I don't have chakra. I am not one of the lucky kids of Shinobi's heritage. They have evolved to mold chakra and distribute it throughout their bodies automatically.

Now, civilians can do the same, provided they start young before their bodies mature completely into adulthood.

Chakra appears to induce mutations in one's DNA safely, aiding in surpassing human limitations.

AI shows the introduction of Chakra made by the visiting shinobi back then.

[Chakra: A fusion of physical energy and spiritual energy that allows one to break one's limits and perform wonders.]

That led me to three hypotheses, whose summary is that being a child soldier is the fastest way to grow strong. Making childhood and teenage the golden time for growing strong. After 18, the body can no longer easily grow strong. So, no wonder Kakashi, Naruto, Sasuke and many others in the canon didn't progress as rapidly after they crossed 18.

[Author's note: If you are interested in the mechanics, you can find them at the end of chapter.]

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I made my way back to the orphanage with swollen hands and feet from my exercises. Doing this without chakra is insane because it may cause damage to my body. The reason I do this—

SMACK

"Kyudo Kirito, how many times will you keep doing this?"

WHOOSH

I felt the surroundings blur as with my head burning from the smack to the head, the scolding from my matron kept ringing my head like a drum.

The matron of the orphanage is a retired shinobi named Rimo Kabuki. So, her body flickered to me in a few minutes to the hospital, where I found myself in front of a Medic Nin.

The medic-nin, who is used to seeing me now-days gave me an exhausted sigh, "Alright, time to heal you for a 7th time this week."

BUZZ

I felt my senses in my hands being overloaded as his mystic palm healed me.

Normally, other civilian kids spend most of the first year trying to form their first chakra through meditation, forcing the fusion of spiritual and physical energy in their bodies. It is alright for them to spend a year while taking their time.

But that is not the case with me.

I am now 3 years old, born at the same time as Kakashi. I will take part in the 3rd Shinobi War. This is a fact.

And also, I will not give up on chakra and spend the rest of my life living in fear. Unlike the other civilians, I don't have the luxury of blissful ignorance.

Now, this is the reason I do this painful training.

[Scanning the feeling from chakra being induced into the hands.

Recording the feeling and processing the data.

97

98

Chakra scanned and reverse engineering host's Chakra feeling.

Time remaining: 1 day 23 minutes]

Chakra is like a weird cross between sensations picked by the brain and muscles at the same time. Think of it as a metaphysical organ.

SMACK

A slap on the back of my head made me look up from my thoughts as I saw a 40-year-old Matron who shouted at me, "Why can't you wait like the rest of the brats? You have had swollen and bruised hands for the last month. It's almost like a clan kid, but unlike them, you have no chakra; you are just approaching your limits faster. Wait for chakra to be moulded; then you can start training to be a shinobi."

"No."

"Huh! What did you say, kid?"

I replied, "I am already behind the other kids, and I need to catch up with them, at least in the body. Besides, there is no fear of my actions because the Medic Nin will heal me properly."

It was true. Konoha hospital is that good. If I weren't in Konoha, I wouldn't do this.

Tsunade, a single person, used her talents to surpass the modern world's healthcare.

It was a shock for me to learn that Konoha is currently on the verge of curing genetic diseases. The current Medic-nin can cure genetic anomalies like Down syndrome as long as they find them during pregnancy.

If the modern medicine is like a slut out for your money, Konoha's medicine is like a queen.

The medic who just healed me rubbed my head and went back to looking at the other patients in the OP ward.

"Sigh, why are you in such a hurry?"

Hearing the question from the Matron, I told the truth.

I looked her in the face and said to her with all my heart, expressing my lack of ignorance, "The world is a terrifying place."

——===The next day===——

No matter the place or culture, the orphanages are most likely found on the outskirts. The reason behind this is simple - they choose the outskirts because it is cheaper and can be easily expanded later.

I walked out early morning 6 into the adjacent forest. The punishments from Rimo-san at least didn't bar this. Otherwise, I would have already heard her shouting at me to stay on the premises. Trust me, I heard her voice many times to make my ears tingle for hours.

This led me to believe that she is a sensor and the reason for her assignment to the orphanage.

I sat myself against a tree and sat in the lotus position. I took deep breaths and focused on the morning chirping of birds and flowing water sounds from the adjacent river.

AI.

[Host chakra reverse engineering

Time remaining: 10

8

7

6

5

4

3

2

1

Completed]

Good, Begin simulation

[Host chakra is being simulated.]

It felt like an adrenaline rush from the stomach, spreading from there to my heart, from there to the rest of the body.

It was incredible. My body felt alive, like I had a buffet after a day of fasting and boosted by coffee.

I kept focusing on that sensation until the AI began prompting me.

[Scanning,

Host ATP is being fused with unknown energy in cells and forming Chakra.]

Term it as spiritual energy.

[Task completed.

Spiritual energy from the soul combines with ATP in cells, forming chakra. The newly formed chakra seems to follow the blood and nerves travel the body.]

AI, stop the artificial simulation.

[Simulation stopped]

I still remember it, my simulated chakra flowing through my body, rotating along the blood and lymph (tissue fluid).

It's unbelievable. I can feel my muscles, heart beating, my stomach, blood pumping to every part, even the contractions of the intestine. The chakra is like a fusion between the muscles and nerves. It can receive and send information along with movement.

Hmm, Receive and send information.

AI, examine whether you can perceive information about my body through Chakra.

[Task received.

Checking. Found the task possible.]

Do it.

[Scanning the body, processing the information.

Showing the data in perceivable form.]

"Haha, Unbelievable."

I saw prompts with ECG data, Vitals, brain waves-EEG and even muscle sprains. My chakra is completing the task that took machines worth millions of dollars in my previous life.

No wonder Tsunade can progress the medical field to such a level. She is like a walking super speciality hospital in the medieval world.

[Warning! Chakra is being consumed as the information is being sent.]

Glucose reserves are decreasing.

The body cannot meet the consumption of ATP levels.

Information receival stopped.]

Then an intense exhaustion hit me as if I spent an entire day running while reading mind-numbing medical text.

Chakra exhaustion, though this one is mild. If AI doesn't stop the task, the chakra usage will pull the vital ATP required for normal functioning of the body, causing injury, coma, and even death is a possibility.

Shinobi naturally train themselves to stop from reaching these limits. Of course, they also train to do the reverse in emergencies.

Same as Kakashi did in the canon against Zabuza. He went to the extreme ending of a coma.

It was after a heavy breakfast; I came back into the forest.

AI will show me the current profile.

[Name: Kyudo Kirito Age: 3 year

Knowledge level: Postgraduate general medicine

Chakra: 5 units]

As soon as I moulded the chakra again, I felt more fit and energetic.

It seems my cells adapted to sending out more ATP to fuse with spiritual energy.

There is not much need for me to worry about spiritual energy because of my mental maturity and experiences.

But it's the body I need to train. Thankfully, I can make myself a regime based on my body for maximum efficiency. Thank god for my AI chip.

AI, implant into me Chakra training exercise- Leaf.

[Consuming 1 unit of Chakra.

Implant completed]

I then experienced the memory of attaching a leaf to my forehead, hand, and even feet.

I soon started the exercise by placing the leaf on my forehead. My chakra followed my prompt to move- From Stomach to heart and from there to head.

But my attempt at chakra exercise differs from the simulated memory. My attempt to pull the chakra through the pathway is like pulling an unwilling child to school.

AI, scan me for inconsistency.

[Scanning.

Chakra consumed for exercise one unit.

All functions are normal.

Abnormality found: The body is not familiar with the process of using chakra.

Solution: Body needs repeated attempts to adapt to it.]

Ok. No wonder there. Shinobi clans took generations to change their bloodlines to have an easy extracting of Chakra from cells and send Chakra throughout the body.

Even civilian-born shinobi train till they achieve both mental and physical adaption, aka chakra control.

Unlike them, I have a completed mental adaption. Like Uchiha, where they can observe the chakra and process the jutsu with a glance.

Yes, doing the jutsu is simply Chakra usage after our body adapts to the process. But not that simple to do, as we say in words.

It is like everyone saying a bullet comes from a gun, but not even a single person can make the gun.

The scary part about Uchiha is that they even have physical adaption too. That is both sides of chakra usage.

No wonder, in the canon, they were driven to extinction because of fear. Without the Senju as a counterbalance, I can't think the paranoid shinobi can sleep in peace.

Others need years to master these skills, but they can do it at a glance.

Sigh.

I just need to practice. AI calculates the attempts to master this exercise. Or in scientific terms, for my body to adapt.

[Calculating ….

Leaf exercise attempts- 1/1000]

A 1000 attempts at mastery. This is with me cheating. No wonder the exercise follows throughout the shinobi school, taking years to be done.

AI shows Hypothesis 4

[Hypothesis 4: Chakra shaping and nature transformation make up Jutsu.

Now Chakra Shape formation is the apex of chakra control.

Nature transformation is the elements- Wind, Fire, Lightning, Earth and Water.

Now a variety of factors influence each transformation, but the main ones are the bloodline and nature of the chakra. Bloodline is more likely termed for clans like Fire Release in Uchiha and Sarutobi. Water and Earth in Senju.

Chakra nature is the way the chakra flows. If it vibrates, then the chakra nature is lightning.

It's the reason a seasoned sensor can distinguish the chakra nature.]

It's the reason we can train our chakra nature, but the problem lies in changing the way it interacts with others. For example, it's like commanding our hands to vibrate every second while doing work.

AI, check my nature.

[Processing the chakra information recorded.

Nature found to be Fire.]

Fire.

Hmm, check the feasibility from Hypothesis 6-fire

[Hypothesis 6- Fire.

It's the literal burning of ATP as fuel.]

[Feasibility confirmed.]

Simulate the transformation and implant it to me.

[Beginning task,

Time remaining: 3 hours]

I got up and started running. Putting my body through its pace seems to be a good idea while waiting.

AI records the process.

I soon forced my chakra to come out of my hand and willed it to burn. A small fire spark came into existence before I collapsed onto the ground with a burning feeling in my hand. WTF.

[Record completed.

Findings: 5 units consumed.

Minor degree burns throughout the hand.

Expected time to heal= 7 days.]

Starting chakra transformation in chunin rank is understandable because anyone below that rank has too low of reserves and a weak body to handle the aftereffects.

Sigh

AI.

Estimate the minimum reserves for holdable training in chakra transformation.

[Compiling data and cross-referencing.

Units required: 1000 units.]

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[Hypothesis 1: 

Physical energy is ATP, the smallest unit of biological energy of the body.

Training the body can increase it.

Talent from DNA determines its limits until chakra can expand it under the stress of extreme hard work.]

[Hypothesis 2: Spiritual energy, at least a form of it, is unique to the inhabitants of this world because of the Sage changing the DNA, and it can bind to ATP/Physical energy to form chakra.

The experiences endured by the individual can increase it.

Maturity, emotions, willpower, etc., help in its mobilization and control.]

Now comes Hypothesis 3.

[Hypothesis 3: 

Despite Hashirama's ideals for Konoha to be a haven for children, Konoha persists in training child soldiers.

Konoha's choice is based on practicality - child soliders proves to be more efficient.

Training shinobi at a young age allows villages to identify talents civilians, whose body can't start chakra usage after crossing the age limit.

There is another benefit for children to become shinobi, as they get a rapid increase in chakra.

So more chakra, more limits broken. From the increased limits, a stronger body. So, the body generates more chakra again. A cycle that runs rapidly until the age of 18, where it becomes difficult to break the body's limits easily.

Hence, making the age below 18 the ideal time for chakra growth.

Therefore, training more shinobi at a young age proves to be cost-effective for villages.]