Sleep.
A state of rest characterized by inactivity or the suspension of the senses and all voluntary movement.
With the exception of physical rest, Yashin's rest has long been as far removed from the rest of that definition as possible.
Always semi-conscious, always with his chakra circulating throughout his entire body, driven by his will.
He has no other choice.
His life depends on it.
Nearly six years of indiscriminately stimulating his hormone production have rendered his body incapable of secreting its own hormones again.
Now, for a single molecule to circulate through his body, he must first stimulate his glands and organs with his chakra.
Whether they are peptides like insulin, steroids like cortisol, or amines like adrenaline, everything requires a conscious and extremely precise effort.
The day his body lost one of its most basic abilities was the day he came closest to death in this new life.
Without hormones, there is no metabolism; without metabolism, the body is unable to process energy, which would quickly lead to severe hypoglycemia or metabolic failure.
However, that wasn't the most urgent problem.
The risk of going into life-threatening shock was much more immediate, since without adrenaline or cortisol, the body is unable to maintain its blood pressure.
Even so, death was not a foreign concept to him; but the confusion, anxiety, and depression that suddenly overwhelmed him when his brain chemistry turned into a mess certainly were.
Devoid of any motivation, he didn't even try to do anything to save himself from his impending death; instead, the idea of hastening it seemed more appealing.
If it hadn't been for his meddlesome older sister, who somehow noticed that something was wrong with her always-annoying little brother and made Iruka stop class and take him to the hospital, the grass on Yashin Haruno's grave would already be nearly a meter tall.
The slight stabilization at the hospital was enough for him to start doing something to save his own skin.
But while it could be said that he was motivated and had some experience in manipulating his hormones, controlling the production of his body's more than fifty major chemical messengers—along with over fifty other peptides and local variants—all at the same time, twenty-four hours a day, seven days a week, was something that couldn't be achieved simply with motivation and a little experience.
Even so, after several months lying in bed with the Shinigami breathing down his neck day and night, he managed to recover—partially.
Now, the vast majority of his chakra was no longer used for training or strengthening himself; instead, it served to keep him alive. The internal vision technique he had developed to understand and modify his body toward perfection had become something permanently focused on controlling his hormonal levels. And the meditation, along with his ultra-precise control of his chakra—which he once thought would take him to the top of the world—had to be redirected to create a state of semi-consciousness that would allow him to replace sleep.
However, it wasn't all bad.
His knowledge of his body and his hormones would never have reached the level it is at now if he had never fallen ill. The same could be said of his fine control over his chakra.
Though such trivial advantages seemed to Yashin like little more than shit.
A pathetic attempt at consolation.
Despite all its drawbacks, after several months, one could say that Yashin's life had returned to a sort of normalcy.
Eating, sleeping, laughing, or walking were no longer a major problem. It was only a matter of time before controlling his hormonal fluctuations became as easy as breathing.
Likewise, his obvious lack of chakra would resolve itself naturally as he grew older.
Therefore, the most important thing for Yashin right now was to take at least half of his sister's breakfast for himself. After all, as a future student of the legendary Sannin, Tsunade, and a user of the Yin seal, the pik-haired girl shouldn't be stingy about something so simple, right?
Besides, a little more or a little less wouldn't make much of a difference in his development.
Feeling Yashin's sympathetic gaze fix on the flat front of the red qipao she'd decided to give her for her last birthday, Sakura instinctively adopted a defensive posture.
—"What?"
Along with the girl's cautious question, Yashin's green eyes drifted southward, to her narrow hips and shorts.
Immediately, the image of that shapely, rosy buttocks amidst the shower steam flashed through his mind.
— The Sage of the Six Paths is quite fair.
A little more aware of his sister's true potential, Yashin decided to back down a bit and settle for fighting over a third of his breakfast; so, before Sakura could explode over his cryptic comment and inappropriate stare, he made the first move.
…
After a hard-fought battle that left Yashin exhausted but satisfied, Sakura hungry and irritated, and Mebuki with a severe headache and a dining room to clean, the siblings left the house to go to school.
Although the pink-haired older sister was eager to get to class so she could gaze from afar at her newly awakened love interest, thanks to Yashin's pace being comparable to that of a slug in summer, they barely made it before the bell rang.
In the end, the journey turned out to be just as torturous for both of them.
Sakura, consumed by impatience, and Yashin, tormented by his twin sister's constant complaints, always two steps ahead of him.
It wasn't until they were a couple of meters from their classroom door that Miss Haruno finally stopped her rant and gave her brother a break.
Before he could finish fixing his hair and brushing the nonexistent dust off his qipao, Yashin, looking more dead than alive, took the lead and yanked the classroom door open; even so, he barely caught the attention of the brats inside.
They were a pretty busy bunch.
They didn't have time for an arrogant cripple or a hormonal brat with violent tendencies.
That worked out well for Yashin.
Fewer animals causing a ruckus around him meant fewer distractions.
It worked for Sakura, too—or at least it did until her panties started getting wet because of the spoiled emo with the "my last name makes me better than all of you" look on his face.
As soon as she saw the apathetic Uchiha sitting in the center of the classroom, the pink-haired girl's eyes flashed like those of a wild beast that had finally found its prey, but even though she wanted to run toward him and cling to him like a leech, she clenched her fists and forced herself to walk toward Yamanaka, who was also watching Sasuke's movements, though much more subtly.
For his part, Yashin barely noticed any of his classmates before starting to make his way to his seat.
At first, anomalies like Hanabi Hyuga, Natsuko Uzumaki, or Sarada Uchiha always managed to claim some of his attention, but after nearly succeeding in his involuntary suicide attempt, even they seemed to lose their charm.
Coming so close to such a stupid death made him realize many things.
In this case, a cockroach has no right to worry about the things it thinks are wrong with the world.
Before reaching the top, the only thing he should be concerned with is himself.
So, paying no mind to the boisterous blond scheming some new prank behind the podium, or his counterpart sitting quietly in the most inconspicuous corner of the classroom; nor the pair of Hyuga sisters with their shoulders almost touching, yet their hearts separated by millions of miles; nor the smiling Sarada and Ino, alongside their group of extras welcoming Sakura; nor the other familiar faces of the supporting characters from his memories, Yashin continued walking toward his seat.