It was the first day of Natsuo's third year at the academy, and he was now in the classroom while the teacher was giving his lesson.
Looking around, Natsuo could see that many faces from last year were missing.
Guessing what had happened, Natsuo knew that the missing children had graduated early.
Following Nawaki's example, these children wanted to become ninjas and go on 'cool' missions.
When last year ended, Natsuo had seen the Uchiha clan children, who had been his classmates last year, proudly displaying their ninja headbands and puffing out their chests.
Natsuo laughed when he remembered that shortly afterwards he saw them chasing cats, painting fences, or walking the Inuzuka clan's dogs.
The only Uchiha child who was spared from suffering D-Rank missions was the boy who awakened his Sharingan, as he joined the Uchiha Police Force after graduating.
As many students from Class A had graduated, there were now many new faces who had been part of Class B last year.
Next to Natsuo, Minato was paying attention to the teacher.
Although Minato had the grades to graduate, he did not do so because his teacher was busy most of the time.
While going back and forth to the hospital, Natsuo met Minato several times and learned that Jiraiya had returned for a short time and taught him several things before returning to his work.
Bored, Natsuo's eyes stared at the teacher while his mind was busy organizing his knowledge.
Besides always going to the village hospital library whenever he had time, Natsuo also had to organize his everyday memories to efficiently manage his training.
Having already learned everything taught at the academy through the thoughts of other students during classes and recess, Natsuo spent the rest of the morning practicing his Yin chakra manipulation.
While reading the superficial thoughts of the students around him, he also kept an eye out for the chakra signatures around him.
After years of training his Yin chakra and strengthening his spiritual energy, Natsuo was now a sensor ninja capable of detecting chakra signatures from 100 meters around him.
Careful that no one noticed what he was doing, Natsuo left the classroom after the bell rang and announced the end of classes for the day.
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Later that same day.
"...and you must always remain calm to analyze the level of damage to the patient and choose to heal the most serious wounds first," Tsunade said as she healed a ninja with several open wounds on his body.
According to what Natsuo heard, this ninja had been training in the village training grounds and had an accident with an explosive tag.
The ninja was very lucky that the tag exploded a few meters away from him, otherwise he wouldn't have had time to get back to the hospital for help.
While keeping Natsuo by her side, Tsunade took over and began healing him while teaching her student.
First he used a chakra pulse to analyze the level of the injuries and then he concentrated on healing the organs injured by the shock of the explosion.
What about open wounds on the skin?
"And after you've made sure to heal the most urgent things, you can start healing the rest," Tsunade said as she closed Ninja's open wounds on the stretcher.
Of course, Tsunade could do the whole process at the same time, but she had to teach her student to prioritize before increasing her own abilities.
"Mm" Natsuo nodded and then followed behind Tsunade as the blonde went to take another case.
As for the now-cured ninja?
A nurse will handle the subsequent procedures.
"Master Tsunade, can water and earth clones only perform Ninjutsu of those elements?" Natsuo asked before Tsunade approached another injured ninja who was entering through the hospital door.
"Yes, why?" Tsunade said and paused for a moment as another doctor took the patient she was pointing at.
"If those clones could also use medical Ninjutsu, it would be ideal for healing multiple wounds at the same time if there is only one doctor available," Natsuo said, and his words made Tsunade stop for a moment longer.
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Later, Natsuo left the hospital happy because he had learned the Ninjutsu he so wanted.
The Shadow Clone Jutsu.
Although it wasn't the multiple shadow clone jutsu, Natsuo couldn't use it even if he had it in his hand because he didn't have enough chakra to launch that Rank A jutsu.
In contrast, its Rank B version could be used by Natsuo, although it only allows him to create a few clones at a time with his current chakra reserve.
Natsuo was able to learn the shadow clone jutsu from Tsunade because his idea could be of vital importance to the front line in the war.
During a war, each village has too many wounded and too few medical ninjas.
Even the Leaf Village, which has the largest number of medical ninjas, had very few medical ninjas who could not treat all the injured they had every day.
In addition to that, the most skilled medical ninjas, those who could heal the most wounded, were not many in number.
But that could be temporarily solved with Natsuo's idea.
Although each medic will have less chakra with each shadow clone he creates, it won't matter in a war where it was vital to heal the most serious wounds first in order to save someone's ninja career and later they could even return to the battlefield.
Pleased with her student's idea, Tsunade had no problem teaching Natsuo the shadow clone jutsu, as he had sufficient chakra and chakra control.
After telling him about the dangers of exhausting his chakra, Tsunade taught him the hand seals, and Natsuo demonstrated his genius once again by learning the jutsu in 4 attempts.
As the afternoon was drawing to a close and Tsunade wanted to inform the hospital director about the idea of using shadow clones for more serious cases, she let Natsuo leave a little earlier today, and Natsuo had already arrived at the orphanage.
Tsunade had also offered Natsuo the option of living at the Senju clan compound, but Natsuo refused, saying that he liked the orphanage and had many friends there.
Of course, that was temporary and his friends would soon be leaving the orphanage, so Natsuo would gladly accept the invitation at that time.
Tsunade agreed and simply told him to let her know so she could prepare her new home at that time.
Entering the orphanage and greeting everyone, Natsuo went up to his room to take a bath and shortly afterwards came down to help prepare dinner.
As payment for helping in the kitchen, Natsuo learned to cook and could now prepare delicious meals.
Of course, Natsuo didn't cook every day. Only occasionally.
But this time she was happy to learn the shadow clone jutsu and wanted to prepare something delicious this time.
After having dinner with everyone at the orphanage, Natsuo returned to his room and saw the reason why he had refused Tsunade's invitation.
Approaching some things covered with a large blanket, Natsuo pulled the blanket back to reveal two cages containing two large mice.
Gone are the small mice they once were, now grown in size thanks to Natsuo's manipulation.
Seeing that everything was still the same, Natsuo opened his bedroom window to let in some fresh air and went back to the two cages.
After removing the two rats that had been drugged and put to sleep using a jutsu, Natsuo cleaned everything up before putting the mice back in their place.
After clearing and cleaning his work table, Natsuo took one of the 2 mice and checked its condition.
Unlike his other experiments on mice to manipulate their muscles, bones, and tendons, which he released into the forest after returning their bodies to their previous states and sterilizing them, these large mice went through a process of accelerated growth.
Since Natsuo could not continue his experiments without human test subjects, he proceeded with another experiment that he planned to conduct shortly.
Accelerated growth through hormone manipulation.
Knowing that he would be sent as a doctor in the future when the second ninja world war began, Natsuo knew that his current strength would not guarantee his survival.
Even if he is a doctor and does not have to fight in the war, it would be foolish to think that enemies would not attack doctors during the war.