In the ninja world, countless ninjas have died from chakra exhaustion in battle.
Therefore, chakra can be seen as an essential energy component required for the body to sustain life.
Without this energy, the body's functions would cease, leading to death.
While there are various causes of human death, Shiraishi considers death from exhaustion to be the most peculiar.
Although the mystery behind it remains unsolved, the current experimental results have produced some unexpected outcomes, opening a mysterious door to an unknown destination.
A vitality potion infused with natural energy was accidentally injected into a laboratory mouse. After draining the mouse's chakra, the potion briefly replaced chakra as the life energy, maintaining its vital activities for a certain period.
To determine if this was a unique case or broadly applicable, Shiraishi immediately began new experiments.
He took twenty new mice, injected them all with the same vitality potion, then drained their chakra, and placed them in observation glass domes.
Shiraishi observed that sixteen of the mice, despite receiving the vitality potion as an energy supply, died immediately after their chakra was drained.
Of the remaining four mice, one was weak in its limbs, lay limply on the ground, its eyes opening and closing, and soon became still, losing all vital activity.
The second mouse showed a similar reaction to the first, only lasting about ten seconds longer before collapsing motionless.
Next was the third. It was in good health and did not show any signs of weakening despite losing chakra; instead, it was lively and jumping around in the glass dome.
The changes in the fourth mouse surprised Shiraishi even more. After consuming the vitality potion, its body became noticeably larger, and its eyes turned a deeper red, giving off a very dangerous aura.
"This is…"
A lab assistant looked surprised, staring intently at the mutated mouse.
"I didn't expect the vitality potion to have such an effect. It's as if it ingested an energy hormone compatible with its body, unleashing its hidden potential."
Shiraishi gave an objective assessment.
The fourth mouse had clearly begun to mutate in an unknown direction.
And even Shiraishi couldn't predict the outcome of this mutation.
Shiraishi then turned his attention to the third mouse. The previously vibrant mouse suddenly entered a state of decline, and like the first two, lay motionless in the glass dome and died.
Shiraishi opened the glass dome and took out the only surviving and mutated mouse, holding it in his hand for observation.
Shiraishi sensed that the mouse's body was filled with an incredibly abundant natural energy.
While he couldn't guarantee that it wouldn't suddenly weaken and die like the other mice if left for an extended period, for now, this mouse's life energy was very robust, showing no signs of life force depletion.
Moreover, the previous experiment also proved that chakra could indeed be replaced by another energy source to sustain vital activities.
This energy source was related to natural energy.
However, there was a problem: in previous attempts, Shiraishi directly used natural energy to replace chakra as the energy supply for vital activities, which invariably led to the death of all experimental mice.
Yet, natural energy, after special processing and formulated into a vitality potion, succeeded in providing life energy to living organisms.
The experiment's result, showing that the human body can sustain vital activities even without chakra, was a success.
So why couldn't raw natural energy serve as life energy? And why could the vitality potion, processed multiple times, achieve this?
Returning to the core of the problem: without chakra, human vital activities cease; specially processed natural energy can replace it.
Chakra does not originate from external sources; rather, it is a combination of the body's physical and spiritual energy. In a sense, it is also a product processed by the human 'factory.'
Confirming the correctness of the experiment indeed made Shiraishi happy.
It also meant that the process of breaking the Caged Bird Seal was one step closer.
However, the correlation between chakra and natural energy increasingly puzzled Shiraishi.
Comparing the two energies, there was an indescribable sense of incongruity.
"I always feel like something very important is missing here. Only by finding this missing piece will all the problems concerning chakra and natural energy be resolved."
Unfortunately, Shiraishi had no clue what this 'thing' was or where the answer lay, so he could only speculate wildly, constantly seeking alternative paths to prove the existence of that 'thing.'
◎
Afterward, Shiraishi devoted himself to researching how natural energy could replace chakra to sustain human vital activities.
If this experiment was merely a vague conjecture before, after that day's unexpected discovery, Shiraishi was confident that replacing chakra with natural energy to provide the body with essential life energy had great feasibility.
Since the experiment itself didn't require high operational difficulty, Shiraishi assigned it to the five experimental assistants, who were responsible for recording the detailed experimental process.
Shiraishi, meanwhile, continued to practice the Spirit Transformation Jutsu, further mastering the ability of Yin Release nature transformation.
Time imperceptibly arrived at the end of August, and the weather gradually became hot.
It had been almost a month since their return to Konoha.
During this month, Shiraishi and his two teammates had exchanged letters with their squad leader, Hatake Sakumo, who was on a mission at the front lines, to understand each other's current situations.
Sakumo learned that Shiraishi and his two teammates had unexpectedly fallen into a trap set by Sand ninjas. After an extremely fierce battle, the three managed to escape the Sand ninjas' trap.
However, due to severe injuries, the three had to return to Konoha for recuperation, with a recovery period of two months.
As for other matters, not a word was revealed.
Sakumo's letters mostly expressed concern for them, and also mentioned that his mission was progressing smoothly. He had successfully destroyed an important Sand hidden base, regaining some advantage for the Konoha ninjas on the front lines.
Currently, the morale of the Konoha ninjas on the front lines was slowly rising, while the Sand Hidden Village seemed to be losing momentum.
It was believed that it wouldn't be long before Konoha and Sand Hidden Village would sit down for negotiations, ending this war peacefully and bringing a perfect close to a conflict that had lasted several years.
Although Sakumo tried his best to describe the front-line situation as relaxed, Shiraishi and his two teammates knew this was merely Sakumo's reassurance; the front-line situation was far from optimistic.
However, as long as Sakumo was safe, Shiraishi and his two teammates were relieved.
◎
"The village is much quieter than before."
After lunch, Shiraishi went out with Ruri, strolling together through the streets of Konoha. Noticing that the crowds were much sparser than usual, Shiraishi sighed.
This was mostly still related to the war at the front.
Konoha had consecutively experienced two wars, with Amegakure and Sunagakure. Although Konoha achieved ultimate victory in the war with Amegakure, it was consequently weakened and needed time to recover and develop.
As a result, Konoha's recovery period was short. In this state of fatigue and extreme laxity, Sunagakure provoked a conflict, forcing Konoha to hastily prepare for battle.
In the conflict with Sunagakure, both sides had victories and losses, reaching a stalemate until now, without a satisfactory outcome.
Sunagakure hoped to plunder as many resources as possible within the Land of Fire to develop itself.
Konoha, on the other hand, hoped to exert pressure on Sunagakure from the front, forcing them to sign a peace treaty and end the war.
This was an intractable problem; it simply depended on who would give out first.
Ruri didn't pay much attention to Shiraishi's sigh.
"How's work going?"
These days, Shiraishi had been holed up in the lab, rarely showing his face outside, only coming out for meals.
Ruri also had her own things to do during the day and generally didn't have time to inquire about Shiraishi's situation.
Shiraishi knew Ruri was referring to the Sage Art research, so he replied, "The success rate has increased somewhat, but the risks have not yet been eliminated. If used rashly, you would end up like you did that day."
Ruri nodded.
That day, she forcibly merged the chakra and natural energy within her body to form Sage Art Chakra, intending to amplify the power of her Fire Style jutsu. It seemed successful at first, but problems arose afterward.
The Sage Art Chakra in her body began to riot, and her consciousness fell into a deep coma. If Shiraishi hadn't performed surgery in time, she would have been in grave danger.
Therefore, Sage Art in that state could be considered a failure and could not be used as an example of success.
However, recalling the incredibly powerful and abundant feeling in her body after merging with Sage Art Chakra that day, Ruri felt a very strong longing.
The power of Sage Art was extraordinary. From the Fire Style she released with Sage Art Chakra that day, one could see that Sage Art could completely transform a ninja, leading to a qualitative leap in their strength.
Most importantly, her Sharingan had now evolved into the Three Tomoe form, reaching the peak of a normal Sharingan, and had essentially lost the possibility of further evolution.
There were two paths she could take next.
One path was to obtain the method for activating the more advanced Mangekyo Sharingan from the Four Elders, further elevating the power of the Sharingan.
The other path was Sage Art.
And Sage Art held greater significance in Ruri's eyes.
Because Ruri didn't have an intuitive understanding of the Mangekyo Sharingan's power, while Sage Art was a power she had personally experienced.
Moreover, the person who had once defeated Uchiha Madara, a Mangekyo Sharingan user, was none other than the First Hokage.
Among the First Hokage's secret techniques, besides Wood Style, there was the mysterious Sage Art.
Sage Art was definitely a power no less formidable than the Mangekyo Sharingan.
Although Ruri was eager, she also knew that mastering Sage Art was not an easy task, so she had never urged Shiraishi, avoiding putting too much pressure on him.
"Let's go look over there. I want to buy some clothes."
"Okay."
Shiraishi had nothing to buy and simply followed Ruri's lead.
This was a traditional clothing store with an excellent reputation in Konoha.
As Shiraishi accompanied Ruri inside, he unexpectedly spotted a familiar face.
"Uchiha… and Chiba-kun?"
A man in his late twenties, wearing a Konoha ninja headband, looked at Shiraishi and Ruri entering the clothing store with a look of surprise.
"Fujimura-sensei?"
Shiraishi also recognized the man's identity: his homeroom teacher from first grade until the end of sixth grade—Fujimura Taiga.
He hadn't expected to run into him here.
"Are you the owner of this store, Chunin Fujimura-sensei?"
Ruri, meanwhile, looked at Fujimura with a scrutinizing gaze.
Fujimura's mouth twitched. Teacher was enough; why add the Chunin prefix especially?
"No, it's not. Actually, well…"
Fujimura-sensei scratched his face, looking a bit embarrassed.
"…This is my girlfriend's shop. She temporarily went out for something, and I'm helping her watch it."
"So Chunin Fujimura-sensei also has a girlfriend."
Shiraishi stroked his chin, looking as if deep in thought.
"…"
What was this, the wife calls the tune and the husband follows? Fujimura complained internally.
"Speaking of which, why are you two in the village? I remember your squad leader is Hatake-jōnin…"
"Ah, due to some unexpected circumstances, we are currently on leave in the village."
"Is that so?"
Fujimura didn't dwell on it and began to introduce the clothes in the store to Shiraishi and Ruri.
In this clothing store, there were all sorts of clothes: ninja outfits, yukatas, casual wear, sportswear, etc.
Besides that, there were also many accessories, such as beautifully styled masks and earrings, all looking very eye-catching.
"How about it? The clothes here are all quite nice, aren't they?"
Fujimura said happily.
"So-so."
Ruri said this, but her gaze was fixed on a particular outfit.
It was a kimono whose style and color she found exceptionally pleasing.
As for the price, it wasn't a concern for her.
Shiraishi also saw the kimono and said with a smile, "Now that I think about it, Ruri, I haven't really given you many gifts over the years. If you like it, I'll buy it for you."
Since Ruri provided the funds for research and accommodation, Shiraishi spent very little money. The mission rewards he had saved were more than enough to buy such a kimono.
After Shiraishi finished speaking, Ruri's usually calm and unruffled face quickly flushed red at an astonishing speed.
Fujimura saw Shiraishi, who was puzzled by Ruri's blush, and sighed, saying, "Chiba-kun, you can't just give a kimono to anyone. For a girl, a boy giving her this kind of clothing means a marriage proposal."
"Huh?"
Shiraishi's body stiffened. He sensed… killing intent!
(PS: Went out for yakiniku with a friend and realized it was already 11:30. No, I need to go to sleep quickly…)