The core principle of Monster Strength lay in compression—compressing all the power in one's body and focusing it into a single explosive point.
If a ninja could truly compress one hundred percent of their physical strength into one strike,
then even without using ninjutsu, they could stand at the very peak of the shinobi world.
But reaching that level—total compression—was almost impossible.
Even Tsunade, the foremost authority on monstrous strength, considered it theoretically unattainable.
The human body simply wasn't strong enough to withstand such pressure. Try forcing it, and you'd end up destroying yourself instead.
At her current level, even Tsunade herself could only achieve around forty to fifty percent compression.
"Compressing strength…" On the surface, it sounded simple—but in practice, it was absurdly difficult.
First, it required absolute control over the body.
How could one even measure how much strength had been compressed?
Every subtle detail had to be mastered—something impossible without an intimate understanding of human anatomy.
That was why Tsunade—being both a medical-nin and a member of the Senju Clan, descendant of Asura—was uniquely gifted in this field.
Her chakra was of the Yang nature, filled with life force. This gave her a natural advantage, allowing her monstrous strength to reach unparalleled heights.
"Total compression… huh? I wonder how far I can go," Leo murmured to himself, then began training.
Chasing unrealistic goals meant nothing; it was better to take it step by step. One bite at a time, one step at a time.
According to the scroll, the first step in training monstrous strength was to control one's chakra to coat the entire body's surface.
For Leo, this was trivial.
With his experience using Armament Haki, he quickly completed the first stage—chakra enveloped his body like a shimmering film.
The second step, however, was the true challenge: Compression.
The scroll detailed a special technique for it—
A skill known as Spiral Force (Rasen-jin).
By twisting and rotating one's internal strength like a coiled spring, the Spiral Force compressed and focused power into a single point—resulting in a devastating burst.
"Spiral Force, huh? That's kind of like the principle behind the Rasengan." Leo smirked.
With a proper method laid out, the rest was just a matter of training like a member of the ANBU—relentless and disciplined.
Time passed quickly. Before he knew it, a week had gone by.
During that time, Leo had been using Shadow Clones to train around the clock. With experience shared between them, his progress was impressive.
His grasp over compression had reached roughly ten percent—a small step, but a solid one.
Using two clones continuously to assist his training also doubled his system's accumulated experience points.
He checked his system panel: 800 / 10,000 EXP.
All of it gained through pure, continuous training—his growth rate had clearly increased compared to before.
Still, constant isolation wasn't ideal. As an ANBU member, he wasn't restricted to headquarters—he could now take on actual missions.
With that thought, he left the training chamber.
But just as he stepped outside, a masked figure appeared soundlessly before him.
It was Tengu, an ANBU operative.
Tengu glanced at him and said, "You've really been pushing yourself. A full week locked in that training room… No wonder someone your age has such strength."
In the ANBU, aside from the captain, Tengu was the only one who knew Leo's true identity.
Officially, only the Third Hokage himself was aware of it.
"My strength's improved a little these days," Leo said. "How about a sparring match?"
Tengu's eyes flickered with amusement behind the mask. He'd almost agreed—but then remembered how effortlessly Leo had used the Body Flicker Technique before.
Better not.
Instead, he offered, "If you want to gain more real combat experience, I know just the place."
"Oh?" Leo raised a brow.
Without further explanation, Tengu turned and led him deeper underground.
The ANBU base was vast and labyrinthine, a sprawling network beneath Konoha—wide enough to lose oneself in if unfamiliar with its paths.
Naturally, Tengu knew his way perfectly.
As they walked, they passed several other masked operatives. Most didn't even speak—just a brief nod, or nothing at all.
Some turned away entirely, cold and detached.
That was the nature of the ANBU—anonymity, secrecy, and isolation.
Each member hid behind a mask, stripped of warmth and identity, until they became nothing but tools—machines of silent death.
After weaving through the tunnels, they arrived at a vast chamber—an open training ground carved from stone.
At first glance, it seemed like a simple arena.
But a closer look revealed two shinobi locked in a fierce duel at its center, ninjutsu and shuriken flashing through the air.
Around them, dozens of masked ANBU watched in silence, their presence heavy yet disciplined.
"Are they… dueling?" Leo asked quietly.
"Mm. Internal sparring," Tengu explained. "No fixed rules. Since no one knows who's behind the mask, they can fight freely. Just don't kill or cripple your opponent on purpose."
Leo smirked. "So basically… an underground cage fight, huh?"
Tengu chuckled faintly. "You could call it that—but it's sanctioned.
The ANBU has a total of one hundred and eight members, divided into three squads, each led by a jonin-level captain.
There are thirty-six jonin in total—the rest are Chūnin, Elite Chūnin, or Special jonin.
To encourage competition, the Captain established a ranking board—the Dark List—which ranks members based on their duel performance."
He pointed toward a stone pillar nearby.
Etched upon it were rows of mask symbols, each representing a codename and rank.
Leo's eyes traced the list—
Rank 1: White Fang.
No surprise there—Hatake Sakumo, the current ANBU Commander.
Rank 2: Red Sun.
An unfamiliar name.
Rank 3: Orochi.
The moment he saw it, Leo's mind clicked.
Orochimaru.
Of course—one of the Legendary Sannin, and once a sub-captain of the ANBU. How could he have forgotten?
I just hope that guy doesn't take an interest in me, Leo thought wryly.
Then again, this was before Orochimaru's descent into madness. Probably nothing to worry about… yet.
Still, caution never hurts anyone. He made a mental note to stay alert around that one.
"So," Tengu asked, watching him from the side,
"Do you want to try your luck in the ring?"
Leo's lips curved slightly beneath his mask.
Why not?
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