Kekkei Genkai was the fusion of two elemental natures. Fire and Earth made Lava. Wind and Water made Ice.
But Hiden—Secret Techniques—were different.
Tonbo sat in the Intel Library, recalling Shikamaru's explanation from the anime. Hiden wasn't about elements. It was about the fundamental building blocks of chakra itself: Yin (Spiritual Energy) and Yang (Physical Energy).
Normal chakra required a perfect 1:1 balance. Mold too much physical energy, and it wouldn't form. Mold too much spiritual energy, and the jutsu would collapse.
But the clans of Konoha—the Nara, Akimichi, Yamanaka—had found a way to break that rule.
"To create a Hiden," Tonbo muttered, scribbling a formula, "You have to skew the ratio."
The Akimichi flooded their chakra with Yang energy to expand their cells. The Nara and Yamanaka flooded theirs with Yin to manipulate shadows and minds.
The danger lay in stability. If the ratio was off, the dominant energy would consume the weaker one. A Yin-heavy imbalance could shatter your own psyche. A Yang-heavy imbalance could cause cellular collapse.
"I need a high-Yin ratio," Tonbo concluded. "My sensory and Genjutsu talents are Yin-based. If I can stabilize a 7:3 Yin-Yang ratio, I can create a chakra signature that bypasses physical defenses entirely."
But he needed guidance. He wasn't arrogant enough to try experimental chakra molding without a safety net.
He finished his shift and headed to the Captain's office.
Knock! Knock!
"Come in."
Tonbo opened the door to find Inoichi Yamanaka standing with a blonde figure in a white cloak.
"Lord Hokage."
Tonbo bowed deeply.
"Tonbo," Minato smiled warmly. "I came to check on Inoichi, and I wanted to clarify some details from your report on the Mist."
"About the transport route?" Tonbo asked.
"Yes."
Minato asked specific questions. Time of day, terrain features from the prisoner's memory, the specific formation of the Kiri guards. Tonbo answered with precision, reconstructing the memory verbally.
Minato nodded, satisfied. "Your attention to detail is remarkable. Lord Third was right about you."
"Lord Third?" Tonbo blinked.
"He mentioned you," Minato said. "He called you a young man who truly understands the Will of Fire."
Tonbo felt a sweat drop form. The Professor really was watching me.
"Thank you, Lord Hokage."
Minato smiled once more, then placed a hand on Inoichi's shoulder.
Zap.
He vanished. No smoke, no sound. Just gone.
"Is that..." Tonbo stared at the empty space.
"The Flying Thunder God," Inoichi said with a hint of awe. "A forbidden jutsu created by the Second Hokage. Only Lord Fourth has mastered it."
"I'm envious," Tonbo admitted honestly. "I want to learn it."
"Hah, don't dream too big," Inoichi chuckled. "It requires a specific chakra signature and reaction speed that defies logic. But... you said you had a question for me?"
"Yes, Captain. It's about Hiden development."
Inoichi's expression turned serious. "That is dangerous territory, Tonbo. Messing with your chakra ratios can leave you brain-dead or crippled."
"I know. But I've hit a wall. I need to know how to stabilize a Yin-heavy mixture without losing cohesion."
Inoichi looked at the boy. He saw the determination in his eyes.
"Sit down," Inoichi sighed. "I can't teach you the Yamanaka clan secrets. But I can explain the theory of Yin Release stabilization..."
Time moved quickly in the reconstruction era.
With the war over, the village breathed easier. Rationing ended. Explosive tags and high-grade steel appeared in civilian shops again.
Tonbo became a jack-of-all-trades. When there were no minds to read, he took odd jobs. He sorted files for the Hokage. He patrolled the streets.
He even stood guard at the Main Gate.
"So this is what Izumo and Kotetsu feel like," Tonbo mused, leaning against the gate post. "It's surprisingly boring."
Ayame was thrilled, though. She brought him bento boxes every day for lunch.
Tonbo ate happily, fueling his grueling training regimen.
He was pushing himself. His Genjutsu was becoming nasty.
In sparring sessions, he tortured his teammates. Seishi, Guy, and Ebisu learned to dread the Despair Pulse and the Memory Seed. Even Guy, with his boundless optimism, could only handle a spar every few days before the lingering phantom depression became too much.
Clang!
Tonbo's kunai was stopped cold by a short white blade.
"You lose."
A masked boy with silver hair stared at him calmly.
"I still can't beat you, Kakashi," Tonbo sighed, raising his hands in surrender.
Kakashi Hatake lowered his White Light Chakra Sabre. The Sharingan in his left eye spun slowly before fading back to black.
"It was the Sharingan," Kakashi admitted quietly.
He was surprised. Tonbo's Genjutsu was subtle and layered. Without the Sharingan's ability to see chakra color, Kakashi might have fallen for the initial feint.
"Hah. A ninja doesn't make excuses," Tonbo said, wiping sweat from his forehead. "If we rely on anything, it should be our brains."
"If you want to talk about fairness, tell the enemy not to use forbidden jutsu."
Kakashi looked at him, surprised by the pragmatism.
"However," Tonbo grinned, a dangerous glint in his eyes. "Next time... your Sharingan won't save you."
Kakashi stared at him. Who gives him this confidence?
The Sharingan was the ultimate counter to Genjutsu. It saw through all illusions.
"My eternal rival! You finally fought Tonbo!"
Might Guy exploded from the bushes, tears of joy streaming down his face. "I will run five hundred laps around the village to celebrate this youthful clash!"
Tonbo's face went blank. This guy really is an anime character.
Kakashi sighed, pulling out a small orange book. "You're noisy, Guy."
Tonbo looked up at the sky. It was blue and peaceful.
But he knew the calendar.
It was almost October.
The Nine-Tails was coming.