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...

Perhaps due to fatigue, Naruto only thought about it the next day.

"Naruto, you are the only one I can trust..." — these words were said to him by Itachi.

With such a serious illness, is Itachi really going to Naruto instead of Tsunade or anyone else? Naruto may be called a genius, but he's not the best. Tsunade might have a way to cure Itachi's illness, yet Itachi came to Naruto with it. Why?

If Naruto had answered Itachi's question differently, asking "are they friends," would Itachi not have confessed about his illness?

"Ugh, it's annoying..." — Naruto sighed heavily and scratched his neck. He definitely has too much on his plate lately, first Ka-chan's illness, and now Itachi and the whole Uchiha Clan, which doesn't exist anymore.

The guards patrolling the gate leading to the Uchiha Clan's area silently let Naruto in, probably already informed of his visit, so they didn't give him any trouble.

In his thoughts, Naruto debated what to do. The desire for knowledge urged him to try to find out what was happening here, but logic told him to back off and deal with his own issues.

He hesitated for a moment, but abandoned the idea at the last moment and continued walking, ignoring the two Chunin.

It's not his business; forget about it all and don't risk angering the monster who created it. If someone was able to keep this secret from everyone's eyes, even the Hokage himself, Naruto prefers not to cross him. If Naruto had discovered it before Kushina's illness, he might have risked it, but now he can't afford to.

Alone now, Naruto politely knocked on the door, and after a moment, Mikoto opened it for him.

"Naruto? It's good that you're here; Itachi informed me of your visit" — Mikoto smiled at the visit of her oldest son's friend.

"Yes, I brought him some things he asked for, I won't stay long" — Naruto explained.

"I understand, you're probably busy now, thank you for still thinking of my son" — Mikoto sighed sadly at the thought of the tragedy in the Namikaze family. They really have had a lot of bad luck in their lives.

"Itachi is in his room, he asked me to take you there, probably still sleeping, he's been quite lazy lately" — Naruto chuckled awkwardly at Mikoto's comment. Itachi probably hasn't told anyone about his illness yet, except Naruto, who is supposed to help him treat it.

After a moment, entering his room, Naruto saw him patiently waiting for his arrival.

Without a word of greeting, Naruto sat on a nearby chair, facing Itachi, and then pulled out medicines prepared for him from the bag.

"I've written detailed information about the microscopic inflammation of the vessels so you know exactly what you're suffering from, and here are the instructions on how much and what you should take..." — Naruto handed his friend several sheets of documents and instructions for the medications he was taking.

"Thank you" — Itachi replied, expressing his sincere gratitude.

"Tell me, how long will I be able to live taking these medicines...?" — Itachi asked.

"If you fully give up being a Shinobi and using Chakra, which weakens your body's condition, you might live to be forty. In my opinion, however, you should turn to Tsunade-sama; she is definitely better than me, and she might find a way to completely cure your illness" — Naruto explained calmly, and Itachi immediately rejected the idea, shaking his head.

"I turned to you because only I can trust you; no one else should examine my body..." — Itachi said, not averting his gaze from Naruto.

"As you wish, I won't interfere in your affairs" — Naruto declared his stance on the matter. It was also a quiet confirmation that he wouldn't meddle in what was happening in the Uchiha Clan.

"Thank you again, Naruto."

"Don't mention it, you know I owe you a few favors" Naruto waved his hand. They were also friends; a few words didn't matter; they just helped each other when the situation called for it.

...

"Earlier, we thought those purple spots were a result of the disease, but maybe they are the disease? They don't directly reduce Life Energy; we confirmed that earlier, but they may have some impact on the body, forcing it to decrease vitality..." — Naruto wondered aloud.

When a piece of skin is cut off with a purple spot, it always disappears, leaving the skin's pure color, like Kushina's. The conclusion is that the spots disappear when they lose their source of vitality, meaning they will all disappear when Kushina dies, no longer having Life Energy in her. 

Examining them, nothing special can be detected in them. They somewhat resemble ink for Fuinjutsu and end on the first layers of the skin. They're a bit like tattoos.

One of the first ideas for curing Kushina was to cut out the skin with purple spots, but they quickly regenerate or appear elsewhere. This shows that they are not the main cause of the disease, but only a consequence. However, there's nothing strange in Kushina's body; she was scanned from every angle and found nothing. Absolutely nothing strange.

Naruto spent long hours using his sensory perception to examine these spots, trying to get to the bottom of the disease. The only thing he discovered was a strange aura he had never seen or felt before.

It was permanent, colorless, and mysterious. That's how Naruto could describe it in a few words.

Trying to search for clues, Naruto compared the auras of all the diseases the patients had in the hospital. However, the auras of diseases were usually dark, evoking sadness and sorrow, trying to devour the positive energy a person possesses. The difference was that the aura of these purple spots was colorless, without characteristic features present in every aura.

Naruto also learned that each type of illness has a characteristic feature in its aura. Neurological, infectious, cardiac, metabolic, psychiatric, endocrine, gastrointestinal, ocular, respiratory, blood, lymphatic diseases, as well as rare or autoimmune diseases, and many others... each of them has some characteristic feature specific to its type, allowing Naruto to roughly determine what the patient is suffering from.

Naruto attempted to discern some detailed information from the aura, such as the characteristic features of the disease, but the aura didn't contain such specific details.

Tsunade was better able to examine Kushina on a medical level, so what Naruto could do wasn't any better. His medical knowledge didn't compare to Tsunade's in any way. The only thing he could somehow help with was his sensory perception, but at the current level, he had already done everything he could in examining Kushina's health.

Naruto thought about strengthening his sensory perception to more thoroughly and accurately examine the reasons for the appearance of these purple spots on Kushina's skin, but he wasn't sure if he could reach a higher level in this field. Currently, he had the best sensory perception in the entire Leaf Village, perhaps even in the world, thanks to his brain mutation, so he didn't know how to elevate it further. It's possible to try to expand it more, but he doesn't know if he can use it to examine something in detail.

Time is also a problem; even if he manages to raise his sensory perception to another level, when will that happen? In a year? Two years? That's definitely too long...!

Another idea for curing Kushina was attempting to stop the decreasing Life Energy. Tsunade wanted to try sealing Life Energy using Fuinjutsu. Minato and Jiraiya created a seal specifically for Kushina, but it didn't work, despite being well-executed.

Hearing about this seal, Naruto thought about using it on himself, but its function was to stop the diminishing Life Energy caused by the disease. Kushina's disease didn't decrease, but rather dispersed Life Energy from her body more precisely, and the seal was supposed to stop it. It caused the cessation of escaping vitality from the body, forcibly keeping it in the body.

It wasn't possible to seal directly the diminishing Life Energy due to aging. It was only possible to stop its dispersal, which occurs due to, for example, illness, as in Kushina's case.

It was a bit complicated, and Naruto couldn't fully understand it at first. Fuinjutsu is a strange and very complex art.

...

In the main library of Konoha...

Naruto spent time in the medical section, absorbing all the information he came across. He wasn't looking for anything specific; he absorbed everything he could, hoping to come across something groundbreaking or a simple clue that would lead him to a breakthrough in his research.

He concluded that he needed to quickly increase his knowledge; it was definitely more important than trying to elevate his sensory perception to the next level.

Kushina's disease is something new they don't know about yet, so there's no point in looking for something even Tsunade can't find. Naruto needs to increase his knowledge beyond what Tsunade knows and also develop in areas of science she hasn't even heard of.

Since he can't do anything right now, the best choice for Naruto will be to focus on learning. Everything can be explained and solved, but it requires having the right knowledge and skills. Kushina's strange disease is a simple proof that they don't possess such knowledge.

Many days later, Naruto realized something. He wanted to train his sensory perception to elevate its level even higher, so he can do it now!

He can accelerate his reading process again, using his sensory perception! It's brilliant! Why didn't he think of it earlier?

The biggest waste of time for Naruto in reading is flipping through pages. If he could accelerate this process even more, Naruto might need only half a minute to read the entire book and absorb its knowledge. To further speed it up, he needs to bypass the movement of flipping pages, and his sensory perception is needed for that.

He can focus his sensory perception on the book and try to read pages from closed books through it. He would simply send his sensory perception into the book, analyze each page sequentially, and his brain would absorb the knowledge.

This will help him elevate his sensory perception to a higher level, but it will be quite difficult. Sensory perception doesn't work the same as echolocation; Naruto doesn't see the surrounding world in his mind by receiving reflected sounds, but detects things in his range such as Chakra or Life Energy. It detects various energies, Chakra vibrations, heartbeat, blood flow, etc. It doesn't directly see physical things unless he concentrates on them heavily.

However, the physical things he can see are really small, but if Naruto managed to remember with his sensory perception what ink looks like, he could read books with his sensory perception.

If that ink had Chakra in it, it would be even easier; well, it can be arranged. It will definitely help him at the beginning, and slowly he will be able to learn with his sensory perception to detect not only energy but physical things as well.

Usually, sensory perception doesn't see physical things; it's impossible, but Naruto's brain allows it. For now, they are only small things, but they are strong evidence that he can see more, bigger, and more material things.

...

"Menma-kun, you wanted me to help you with training, right? I'll help you gain better control over your Chakra, so you can surpass your peers even more, what do you say?" — Naruto offered his younger brother help.

"What...? You'll really help me?!" — Menma was very excited, his eyes sparkling with hope.

"I just thought it might help us both in some way" — Naruto chuckled.

In the following weeks, Naruto helped Menma transfer his Chakra into ink and write with it on paper. It was difficult and quite advanced training; just transferring Chakra into ink was simple, but maintaining it while writing was extremely demanding and required immense concentration.

Naruto helped Menma as much as he could, advising him from his experience; it wasn't much, but it probably helped Menma's learning to some extent.

Menma spent a lot of time writing and was very disciplined about doing it every day after academy classes.

Naruto closed his eyes and detected the Chakra in the ink, then his brain analyzed the shape and pattern of the Chakra, translating it into writing. It took him two weeks to start slowly seeing the ink without Chakra in it. His sensory perception was slowly able to remember what ink looks like and naturally detect it.