Naruto didn't encounter Himiko in the corridors of the Academy anymore; she probably hid from him in the classroom, not wanting to get reprimanded in front of everyone. But that didn't matter; he had to straighten her out at home. She had always neglected her studies, not even looking at the books, and he had been too lenient about it before, so now she had to improve.

To not be too harsh, Naruto knows that such an approach with his sister happens because of the excessive amount of Chakra in her small body. As a Jinchuriki of the Kyuubi and a descendant of two great Clans, Namikaze and Uzumaki, Himiko has the most Chakra in the entire Village, which makes it difficult for her to concentrate on one thing. She often thinks about three or four things at once, unable to focus on one for more than a few minutes.

So as soon as he got home, Naruto started a serious conversation with her.

"Umm, Onii-chan?" - Himiko was nervous about his serious expression, her thoughts revolving around his visit to Iruka-sensei and the associated concerns.

"Sit down, we need to talk about your personal development. You didn't think that after what I found out, I would let it slide, did you?" - Naruto ordered, and Himiko obediently hung her head.

"I'll go to my room...!" - Menma quickly disappeared from his brother's sight, not wanting to get into trouble with Himiko.

Himiko sat at the table, across from Naruto, impatiently waiting for what he would say.

Naruto was silent for a moment, observing the enormous amount of Chakra she possessed in her body. Truly, the amount of Chakra was insane; every time he saw it, he couldn't help but shiver.

"From today on, I'll train you, and you must do everything I say, because your future as a Shinobi will be in jeopardy...!" - Naruto warned her, surprising her at the same time. She thought he would start by scolding her for poor grades and forcing her to study, but he talked about training her instead.

"Will you train me like you train Menma-nee...?!" - Himiko couldn't help but stand up.

"Yes, but don't get too excited. It will be difficult... for you, especially. We will focus on meditation and increasing your control over your Chakra, which will improve your focus. This will make it easier for you to absorb the material from the Academy" - Naruto explained, and as he expected, Himiko's expression darkened.

Wanting to provoke her a bit, Naruto smiled mockingly, "Menma-kun and I find it easy, do you think you can keep up with us?"

Himiko's face immediately twitched at his words. Without much thought, she nodded firmly, and Naruto felt her determination emanating from her. Children her age were quite easy to provoke and manipulate, especially someone as innocent as Himiko... Naruto wasn't sure how to feel about that.

...

Himiko was forced to meditate daily, and she was really... annoyed. She would rather torture herself to death than sit in silence and meditate. It was crazy to her how anyone could sit in such deafening silence and solitude for hours on end. Remembering how Naruto meditated for long hours, day after day, she felt immense admiration and fear towards him.

Even one minute, which usually passed extremely quickly, stretched mercilessly during meditation. Himiko was irritated and impatient; it was really hard for her to sit in one place without thinking about anything. Naruto instructed her to keep her mind empty, without any thoughts, but honestly, all kinds of thoughts invaded her every possible second of meditation, and she couldn't get rid of them. They were also the only interesting thing happening during meditation.

At first, Naruto set the timer for five minutes, but barely two minutes into meditation, Himiko opened her eyes, asking how much time had passed. Naruto had to scold her for being distracted and reset the timer; the second time she lasted the full time, but then she had to get up and do something because she was getting irritated at the thought of doing it for even one more minute.

On the same day, Naruto forced her to meditate twice, for five minutes each time. At first, she had to get used to the silence, and most importantly, to herself, during meditation. Many people with loud and energetic personalities couldn't stand being alone with themselves for more than a few minutes, and it was the same with Himiko. She had to get used to being alone with herself and accept it. Naruto talked to her for a long time after the meditation session, trying to speed up this process by making her realize a few things.

And so, after a week, her meditation time increased to ten minutes. Maybe she hadn't rid herself of unnecessary thoughts during that time, but she was able to endure that much time without getting distracted. Himiko may not have noticed it, but unconsciously, her thoughts became clearer, more distinct, and coherent with each passing minute of meditation.

Naruto helped her with her lessons in the evening, and they also reviewed the material from the first year of the Academy together. Those were simple topics and only required refreshing, and for the more difficult ones, Naruto helped her understand.

In their free time, Naruto helped both of his siblings with Chakra control exercises. Menma was at a more advanced stage, while Himiko had just started. She was quite excited about the training at first, but quickly realized that it was as boring and irritating as meditation. However, seeing Menma working hard, Himiko didn't want to give up.

Naruto had a lot of free time since he had elevated his reading speed to another level. In six months, he had read most of the books in Konoha's main library, which resulted in a lot of free time. He participated in and conducted his own research in an attempt to cure Kushina, but they had tried almost everything, and even he didn't know what else they could do. So, he spent most of his time thinking about what else they could try.

Training his siblings was an additional activity to keep him mentally fit. It was a bit like finding happiness in pain. Kushina certainly wouldn't want them to mourn over her fate. Himiko and Menma surely felt significant worries and fear, but they were able to hide it well, maybe even better than Naruto and Minato. Spending time together, like training, was a kind of bonding in pain and an attempt to find common happiness.

In a few months, Himiko was able to improve her focus, making it easier for her to understand the more difficult topics they were learning at the Academy. Naruto continued to help her, breaking down everything from scratch and explaining the subject from several perspectives to make it easier for Himiko to grasp.

However, the worst subject, or rather the worst area of study, for Himiko was mathematics. Even after a long time, she couldn't understand it, and Naruto really struggled to explain simple operations to her.

"Hmm... I have an idea of how to present it to you, come with me...!" - Naruto took his sister to their home training ground behind the house and pulled out a few kunai from a leather holster.

"We're going to practice target throwing?" - Himiko's eyes lit up with excitement immediately, finally something interesting!

"No. I want to illustrate mathematical principles in practice, it's the best way I've come up with," - Naruto immediately dashed her hopes.

"Oh... too bad, I'm really good at that."

Naruto smiled gently at her, not wanting to crush her self-esteem. "Are you? Then watch!"

In an instant, Naruto threw two kunai, seemingly aiming at random spots. Himiko wanted to snicker with amusement, but after a moment, the two kunai collided with each other, rebounding off each other and hitting two separate targets accurately.

"W-what...?!"

"You see? Look again, this time it will be slightly different."

Naruto threw another kunai, but this time only one, then aimed another at the approximate place of the flight path of the first kunai. The second kunai struck the first one, altering its trajectory, causing it to hit the bullseye.

"How is that possible...?" - Himiko stared at it incredulously.

"This is the realm of Shurikenjutsu, but I showed you this not to brag, but to help you understand why math is so important."

"What does it have to do with this?" - Himiko was confused by her brother's words.

"Mathematics involves formulas and calculations, and what I did was an execution and the final result. It's best to translate this into units, as described in the book. I threw the kunai, for example, with a force of 4 units; you needed a minimum of three units of force to hit the target," - Naruto explained, now demonstrating the example of a throw, using too little force, the kunai didn't reach the target, but with a force of 4 units, it hit the target accurately.

"It's simple, but how does that help me understand the problem?" - Himiko still wasn't convinced.

"In the more challenging materials from the later years of the Academy, you learn how to calculate the trajectory of a kunai, but it's much harder to translate it into your accuracy in practice. Actually, it's impossible because fighting is different from mathematical operations. You don't have the given values needed for calculation; you have to intuitively, in just a moment, consider the wind force, angle of throw, etc. That's why some consider it a bit unnecessary for learning, and well, I partly agree, but you don't have a choice, and you have to understand it, that's what the Academy requires. However, try to imagine it as a help; by understanding how to calculate difficult throws, such as the ones I showed you, you can more easily replicate them. With theory, it's easier to practice," - Naruto elaborated.

"Are you able to hit the bullseye?" - Naruto asked, handing her one kunai.

"Without a problem," - Himiko replied, throwing the weapon. She hit the bullseye practically perfectly.

"4 units is the minimum throwing force for the kunai to reach the target; 20 units can destroy the target, and beyond that, it will pierce through it," - Naruto explained further.

"In your task, the question was whether the kunai can hit the target if there's a strong wind, and we throw it in the same way as we do in normal, windless weather. The answer is yes and no; we don't need to consider the wind force when the kunai has the appropriate force, and the wind is blowing, for example, from the back or front, but if it's from the side, the kunai will involuntarily tilt. A shinobi should always observe the weather and make adjustments," - Naruto reiterated.

"You already said that..." - Himiko groaned tiredly.

"Did I? Never mind, look at this," - Naruto pulled out a piece of paper and began drawing complex calculations on it.

"This is the exact calculation of my second throw, which I showed you at the beginning. Tell me, would it be easier for you to repeat it blindly or with the exact calculation?" 

Himiko scratched her neck. "Um, I don't know, it looks hard."

"Yes, well, of course it does. You have the necessary force given here; you just have to adjust to the action. Let's test it," - Naruto instructed, handing her two more kunai.

"What...? Can I really?" - Himiko exclaimed excitedly.

"Yes, that's what I'm saying. Look at this calculation and tell me what proportions of force you should use."

Himiko looked at the paper and pondered for a few seconds. "The first kunai throw requires a force of 6 units, and the second one requires 18, three times more than the first."

"Exactly, the second kunai must be faster than the first because the first one is already far ahead of it, and if you use the same force, the second kunai won't catch up," - Naruto explained.

"Oh, right. Can I try now?"

"Not yet... Do you know where the second kunai should hit? Look at the calculation; this is supposed to be the flight path line of the first kunai. They are supposed to meet exactly at this point after using this force; you have to adjust everything perfectly, use the right force, and have natural accuracy to aim perfectly at the right point. Analyze it calmly, and when you're ready, throw...!" - Naruto explained, showing her everything in action.

"O-okay..." - Himiko stared at the paper with concentration, then nodded after a while.

"Okay, I'm ready," - she took a deep breath and then threw the first kunai, followed by the second a second later.

"Oh..." - Himiko sighed after a moment, feeling disheartened. She missed.

"It's okay, it's an advanced exercise, and you're only in the second grade of the Academy, try again," - Naruto comforted her.

After several attempts, she finally succeeded. However, when the second kunai struck the first one, instead of flying towards the target, it hit the ground.

"What?! Why?" - Himiko exclaimed, bewildered.

"You see, besides that, there's still much to consider, look, you didn't pay attention to everything, just analyzed what I told you," - Himiko felt disheartened; it was harder than she expected, and her head was already aching from Naruto's explanations.

"You didn't even observe how I moved during that throw. I'll do it again, and pay close attention to the movement of my wrist," - Naruto instructed and pulled out two more kunai. In slow motion, he repeated the movement; the two kunai collided, one fell to the ground, and the other, with greater force than before, hit the bullseye.

"What did you see?" - Naruto asked.

"Oh, I know! During the second throw, you took a half step sideways, which gave you a better angle!" - Himiko immediately responded.

"Yes, but that's not all. I'll show you again, and watch my wrist," - Naruto instructed.

The day slowly passed, and Naruto combined practical training with learning to force Himiko to understand the topic. It worked even better than he expected. Maybe it's easier for others to grasp something when they do it rather than learning from books? Well, maybe so, but Naruto never had trouble understanding such things.