With the help of the system, Uchiha Renji quickly became proficient with shuriken techniques. From a short distance away, both Itachi and Shisui widened their eyes at Renji's rate of improvement.
Both of them were recognized as geniuses among the Uchiha, but even so, their own progress with shurikenjutsu had been much slower than Renji's.
"Shisui-nii, how long did it take you back then?" Itachi asked quietly.
"A week. I'd wager you were about the same, right? But this kid… he's a monster. He only watched once and he's already throwing like that. Looks like our clan has yet another prodigy on its hands."
Renji had no idea that every movement of his was being carefully observed by Itachi and Shisui. Not that he would have cared—both of them were good people. As long as Renji didn't do anything to threaten the safety of Konoha, he wouldn't be in danger from them.
The entire morning was spent practicing shurikenjutsu. It was the only skill he could call his own right now, so he poured himself into it. As noon approached, Itachi and Shisui walked back over to him.
"You did well, Renji," Itachi said. "Next, I'm going to teach you about chakra refinement. Chakra is the energy produced when the body's physical energy is perfectly combined with spiritual energy. It's the source used for ninjutsu, genjutsu, taijutsu, and even things like creating chakra threads to restrain enemies or sever chakra-based constructs."
He spoke calmly, his tone like that of a teacher, despite being just a boy himself.
"This energy is composed of two parts: first, the physical energy extracted from every one of the body's 130 trillion cells; second, the spiritual energy accumulated through training and life experience. Only after refining chakra and forming hand seals can one use techniques."
Itachi laid out the fundamentals of chakra. In truth, the Uchiha clan had scrolls detailing all of this—it was considered basic knowledge. But to him, Renji was only a four-year-old child, far too young to know these things.
"Do you understand what I've said?"
"I understand," Renji replied earnestly. "I've read about chakra theory in books at home, but I still don't know the actual method for refining it."
Itachi nodded, just about to continue—when a voice suddenly called out.
"Itachi, I knew you'd be here. Eh? Who's this kid? He doesn't look like your little brother, Sasuke."
A girl stepped forward.
"This is Uchiha Renji. You could say he's Itachi's… opponent. He's the one who tried to ambush him yesterday," Shisui explained.
"Renji?"
"Hello, Renmi-neesan," Renji said politely.
At the sight of Uchiha Renmi, Renji immediately recognized her—the pretty little girl who idolized Itachi. In the original history, she would perish during the Uchiha massacre at Itachi's hand. For her, perhaps dying inside Tsukuyomi was a form of mercy, sparing her from the cruel reality of dying by the hand of the one she loved.
Ding. System notification: Side quest discovered. Assist Uchiha Renmi in fulfilling her heart's desire. Reward: Unlock special system. Failure: no penalty.
Renji froze. The system hadn't spelled it out, but he already knew from his knowledge of the Naruto timeline—Renmi's wish was to be with Itachi.
"You're amazing," Renmi said with a smile. "To challenge Itachi at such a young age takes real courage. But if you want to beat him, you've got a long way to go."
Strangely, she felt a sense of closeness to Renji, as if he were her younger brother. Maybe their similar names had something to do with it.
"Mm. I know. I'm learning shurikenjutsu from Itachi-nii right now. He's also teaching me about chakra."
"I see. Then you—"
Before long, Renji and Renmi were chatting away happily, leaving Itachi and Shisui standing awkwardly to the side.
"Ahem. Renmi, you came here today to see Itachi, right?" Shisui finally interrupted when the two seemed completely lost in conversation.
"Mm. I brought you all lunch. Eat before you continue training." She pulled a small pack off her back.
"Oh, Shisui-nii, I just remembered—there's something I need your help with. Can you come with me for a bit?" Renji said suddenly, giving Shisui a pointed look.
It was a clumsy attempt, far too obvious. Shisui and Itachi didn't seem to notice, but Renmi did. She realized Renji was deliberately creating a chance for her to be alone with Itachi.
Her cheeks flushed red. On one hand she was surprised at how precocious Renji was, but on the other hand, having her feelings exposed made her shy like any other girl.
Practically dragged along, Shisui left with Renji, leaving Training Ground Seven with only Itachi and Renmi. What happened between them was of no concern to Renji.
"Renji, what did you want to talk about?" Shisui asked once they'd stepped outside the training field. The two began wandering through the Uchiha compound.
"Shisui-nii, you really didn't notice? Renmi-neesan likes Itachi-nii. Why else would she sneak away from her lessons just to bring him food?" Renji said with mock exasperation. Inwardly, he felt bad for Renmi—every time she came, she ran straight into Shisui, the world's biggest third wheel.
"So that's it. Hah. You're just a little brat, but you understand a lot, don't you? Anyway, Itachi was just teaching you about chakra sources. Let me explain chakra nature to you. Chakra has five basic elemental natures: Earth, Water, Fire, Wind, and Lightning. Each has its counter—Earth beats Water, Water beats Fire, and so on."
"I see." Renji nodded, though he already knew all of this. He had to act as though it was all new to him.
"In most cases, a shinobi is born with one chakra nature. Jōnin-level shinobi usually train in a second nature later. You'll learn all the details once you enter the Academy. For now, I'll test your chakra nature. Most of us Uchiha are naturally Fire-type, though there are exceptions."
He produced a thin slip of chakra paper.
"This paper reveals your nature when infused with chakra. Fire will burn it, Wind will cut it, Lightning will crinkle it, Earth will crumble it, and Water will dampen it."
Renji took the slip and pushed his chakra into it. What he didn't realize was that Shisui had deliberately skipped teaching him how to refine chakra. He had noticed small inconsistencies in Renji's behavior earlier and suspected that the boy already knew far too much. This "test" was a way to probe him.
Renji fell right into the trap. He pushed his chakra into the paper with ease.
Shisui's eyes narrowed. So the boy could refine chakra. For a moment, suspicion flared—could Renji be a spy?
But the next second, all doubt was blown away.
The chakra paper split down the middle. One half burst into flame, the other crinkled with the marks of lightning.
"Three natures?!" Shisui gasped in disbelief.
His suspicion evaporated instantly. A child with three innate chakra affinities could never be a spy planted in secret—they were simply too rare.
Even Shisui himself had only been born with Fire and Lightning. While he was working to develop others, his natural limit was two. To his knowledge, the only shinobi born with three elemental affinities was Ōnoki, the Third Tsuchikage. And his legendary Dust Release kekkei tōta had only been possible because he possessed Wind, Earth, and Fire at birth.