"Alright, class. Let's begin today's lesson."
Iruka-sensei stood at the front of the room, chalk in hand. "Last semester, we covered Konoha's history and the Third Hokage's Will of Fire. Hikari, since you missed it, review the material on your own."
"Today, we're focusing on the Chakra Core and the three types of shinobi. Take notes—this will be on the exam! And pay attention to a critical misconception you must understand."
The screech of chalk against the board sent Hikari spiraling back to her high school days—anxiety creeping in on instinct. But the bold words "Chakra Core" snapped her back to reality.
"Chakra is formed by—"
"Hey, Hikari… did you eat breakfast?" Naruto's whisper cut through Iruka's lecture, making her brow twitch.
The Kaguya clan's training had been brutal—chakra extraction, bone dances, live combat. It made her strong, but left her knowledge full of gaps. Especially in this realer version of the ninja world.
Last night, she'd skimmed the textbooks. The first-year material was disappointingly basic, dodging the deeper truths she craved. Might Guy was no help (self-proclaimed "eternal genin," after all). This classroom was her only shot at real theory.
"Naruto, focus." She kept her voice sweet.
"Yeah, yeah!" He nodded—then immediately spun his pen between his fingers.
Click. Clack. The pen kept hitting the desk.
Hikari sighed.
Nothing's free. Scheming for the Nine-Tails' chakra came with a price. Might as well consider this prepayment for an all-you-can-eat buffet later.
"Naruto-kun."
"Huh?" He perked up.
"Could you do me a favor?" She tilted her head, morning light gilding her profile. The shadow of her nose curved delicately over her lips.
"Y-yeah! Anything!" He didn't even hear the request—just stared, dazed, at her mouth.
---
Iruka's chalk screeched again. A quarter of the board was now dense with notes.
"As you know, chakra is a blend of mental and physical energy. The key to synthesizing them? The Chakra Core in your heart—some call it the 'Chakra Seed'."
He paused, letting it sink in.
"The core devours mental and physical energy to grow, then feeds chakra back to the shinobi. Like a seed—we nurture it, it matures.
Since every soul and body is unique, each core develops differently. That's why no two people's chakra are exactly alike.
A ninja's entire power lies within their core…"
Hikari listened, struck by déjà vu.
A miniature Divine Tree.
The Ōtsutsuki planted the tree to drain the world's energy for chakra fruit. Shinobi cores did the same—just on a smaller scale. It also explained why Orochimaru's cloning experiments failed.
Kekkei Genkai weren't about genes. They were about the core. Children inherited a "fruit" from their parents' matured cores—not DNA. Limited fruits meant limited bloodline heirs. And shinobi could choose whether to pass them on.
---
Byakugan: ACTIVATE.
Hikari peered inward at her own core—a swirling deep blue. It hadn't always been that color. After absorbing a fragment of the Three-Tails' chakra, it had… mutated.
"Exposure to foreign chakra can alter the core," Iruka wrote, "which then produces new chakra!"
He dusted off his hands.
Most of the class was slumped over, asleep.
Iruka's eye landed on Hikari—motionless, blindfolded. Had she absorbed any of this? He'd spoken slowly for her sake.
Then he saw Naruto.
And nearly dropped his chalk.
Uzumaki Naruto, the class dunce, was taking notes.
"Ch… a… kra…" Naruto's handwriting was atrocious, but he gritted his teeth, scribbling.
He'd promised Hikari he'd record the lesson for her.
And an Uzumaki keeps his word.
(Even if it was so boring his brain was melting.)
---
Iruka clapped. "Wake up! This next part's essential for exams!"
"Chakra reserves are tied to vitality—the stronger your life force, the more energy your core absorbs, the more chakra you produce.
In other words…" His voice turned grave.
"Your chakra capacity is fixed at birth.
It. Cannot. Change."
---
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