"Now that you've finished your first day of training, I'll give you this as a reward," Tanjiro said, handing Itachi a vial containing a green liquid.
"What is this, Sensei?" Itachi asked, confused and curious about the liquid.
"A serum to unlock your hidden potential. If your potential is high enough, it will awaken your Sharingan up to the three-tomoe stage," Tanjiro explained.
"Is that true?" Itachi asked, bewildered. Such a thing could potentially spark another Ninja World War if it became known.
Despite his age, Itachi understood that the world moved according to the interests of nations. Anything that could elevate a nation's power would lead to wars, negotiations, and more, all to acquire something as valuable as the serum.
"It is true, but you must keep it a secret and never reveal it to anyone else."
"Drink it. Have faith in me," Tanjiro urged. Without hesitation, Itachi drank the serum. Moments later, a surge of chakra erupted around him before condensing within his body. The sudden release of such powerful chakra immediately alerted the sensor ninjas, who reported it to the Fourth Hokage while others moved toward the source.
Sensing the approaching ninjas, Tanjiro frowned and locked onto them, releasing his own chakra. His precise control overwhelmed the sensory ninjas, bombarding their senses with an immense force comparable to that of a Kage.
Their movements halted as a primal fear washed over them, the feeling of a predator's gaze on their backs. Instinctively, they knew they had to retreat, or face certain death.
Then, right on cue, Minato arrived using his Flying Thunder God Technique. Assessing the situation immediately, he ordered the ninjas to disperse.
"It seems you've caused some trouble, Tanjiro-san," Minato sighed, sensing the immense chakra centered around Itachi. Tanjiro remained silent, merely waving his hand as he watched the scene unfold, a glimmer of anticipation in his eyes.
After a few moments, Itachi, overwhelmed by the influx of chakra, slowly opened his eyes. They quivered briefly before revealing the distinct rotation of a three-tomoe Sharingan. At just five years old, Itachi had become the youngest Uchiha to unlock the Sharingan—and not just any Sharingan, but the fully developed three-tomoe form. The serum had also significantly boosted his chakra, elevating it to at least the level of a jonin, enabling him to wield the power of the three-tomoe Sharingan.
At one tomoe, the Sharingan enables the user to read an enemy's movements, enhancing their speed and accuracy.
With two tomoe, the user can effectively imitate others, copy jutsus, and use enhanced genjutsu.
Lastly, the three-tomoe Sharingan allows the user to perfectly imitate someone, instantly copy nearly all jutsus, use advanced genjutsu, and significantly enhance their reflexes.
Throughout history, those who possess the three-tomoe Sharingan are considered equivalent to Jonin-level shinobi. They are feared worldwide for their ability to copy jutsus, perfectly imitate fighting styles, and even predict their opponents' moves. With Itachi now possessing the three-tomoe Sharingan, his strength is at least at the level of a chunin, and with some practice and battle experience, he will become a formidable foe in the future.
"Congratulations on unlocking the three-tomoe Sharingan, Itachi. You've truly lived up to my expectations," Tanjiro said with a smile, watching the three tomoe spin in Itachi's eyes.
Itachi smiled, his expression innocent and joyful. Being praised by Tanjiro filled him with happiness, like a child being commended by his father. Despite being only four years old, Itachi had already witnessed the harsh realities of life when the Third Ninja War ravaged the nations.
Fugaku, his father, had taken him to witness the brutality of the battlefield, preparing him for the future they would face as shinobi—a duty they were bound to fulfill.
But now, in Tanjiro's presence, a sense of innocence resurfaced within Itachi. Unknowingly, he had been influenced by Tanjiro's charisma, allowing his inner child to emerge once more.
"Mhm, thank you, Sensei. Hello, Fourth Hokage," Itachi said, bowing his head respectfully as he looked at the two figures who held a special place in his heart. Minato, known as the Yellow Flash of Konoha, was a legend. His feats during the war were recognized by all ninjas and the great clans. Itachi knew how powerful Minato truly was, and the fact that someone so feared and respected was a friend of his teacher and father filled him with pride.
Though strength was paramount, Itachi understood that connections were just as important. Properly used, alliances could provide access to rare jutsus and wealth. However, he also knew that such things wouldn't concern his father, Fugaku, who, like many Uchiha, was proud and saw little value in relying on others.
As an Uchiha, Itachi was well aware of their clan's stubbornness and pride, especially when it came to forming bonds outside their circle. Only a select few, like Shisui, saw the value in connections. Shisui, a prodigy and master of the Body Flicker Technique, had become close to Itachi by offering to train together. Through that bond, they had grown closer, eventually becoming best friends.
That was until Tanjiro arrived, whose charisma naturally influenced those around him. Itachi began to think of ways to convince Tanjiro to have him and Shisui train together.
"Since we're done with training, I'll take you home. Otherwise, your mother will be looking for you everywhere. Let's go, Itachi. Minato-san, I'll return this kid to the Uchiha Compound. Wait for me at your house," Tanjiro said. Minato nodded as Tanjiro pulled Itachi to his side.
Without forming a single hand sign, Tanjiro used the Body Flicker Technique, and in a brownish-red flash, they were gone. Even Minato, with his renowned speed, couldn't keep up with Tanjiro's movement.
Through constant total breathing, Tanjiro's body and mind were profoundly influenced by the chakra, allowing him to achieve balance. This meant he was growing stronger and faster by the second; the longer he stayed in this world, the more his power increased.
Soon after, the two of them arrived at the Uchiha Compound, where Tanjiro gently dropped Itachi off, waving goodbye.
Itachi waved back as he entered the compound. Once Itachi was out of sight, Tanjiro made his way back to Minato's house. Upon his arrival, he found Kushina sitting on the sofa, relaxing and tenderly rubbing her bulging belly.
"Hello, Kushina-san," Tanjiro said with a slight smile as he greeted her. She waved back, beckoning him to come closer.
"Hi, Tanjiro-san. How was your day as Itachi's teacher?" Kushina asked.
"It was better than I expected, honestly. That kid is a genius; he easily learns what I teach him, and he is persistent and consistent with the tasks I've given him. I must say, I'm quite looking forward to the future when he gets older," Tanjiro replied, reflecting on Itachi's potential.
"That's great to hear, Tanjiro-san. By the way, do you want to feel Naruto?" Kushina said, lifting her shirt to reveal her bulging belly. Tanjiro smiled and approached her, placing his hand gently on her stomach.
As soon as he made contact, he sensed two distinct sources of chakra: a massive one and a smaller one. The massive chakra was unmistakably that of the Nine-Tailed Fox, Kurama, which Tanjiro recognized. From what he could sense, this immense chakra was filled with a sinister energy that could overwhelm a person.
Tanjiro closed his eyes and directed his chakra toward the powerful force he sensed. When he opened his eyes again, he found himself staring at a large cage, and within it, a nine-tailed fox glared at him with murderous intent.