"Yin Seal—Release!"
Tsunade's guess had been completely correct.
After distributing too much chakra to the wood clones that were studying sealing techniques,
Ren—whose remaining chakra had fallen below thirty percent—didn't hesitate to release the Yin Seal.
Over the past few days, relying on his incredibly fast chakra recovery speed,
he had continuously stored chakra inside the "mysterious pool" of the Yin Seal.
The accumulated amount had already become astonishing.
At the very least,
it exceeded ten times his normal full chakra reserves.
More than enough for him to spend freely.
"Multiple Wood Clone Technique!"
In a deserted forest,
Ren shouted.
Swish—swish—swish—
Countless wooden vines rapidly grew.
In the blink of an eye,
more than a hundred wood clones appeared.
"Brothers, for the sake of our happy life tonight…"
Ren said dramatically,
"I'm counting on you!"
He drained most of the chakra stored in the Yin Seal.
Each wood clone was assigned roughly twenty percent of his full-state chakra.
That was far more than the clones left at the inn studying sealing techniques.
Each clone had chakra comparable to 1.5 Tsunades… and several Kakashis combined.
This wasn't like Naruto's half-baked shadow clones in the original timeline.
Those fragile clones were practically made of paper.
If he wanted,
Ren could easily create hundreds or even thousands of wood clones.
But that wasn't necessary.
For him,
wood clones that retained substantial combat power and abundant chakra
were the most efficient training model.
"This is the Flying Thunder God formula I designed. Practice using this!"
Ren carved a special symbol onto a large tree.
It was the pattern of his Mangekyō Sharingan.
"Every ten minutes, we'll activate shared mode and synchronize our training results."
This was a system Ren had developed over the past two years.
A shared training mode built upon his wood clones.
His original body functioned like a central memory database.
Without needing to dispel themselves,
the clones could upload their memories, experiences, and insights back to him.
Ren, acting as the central processor,
would analyze the information,
eliminate incorrect training methods,
and organize the most efficient solutions.
Then he would redistribute the refined knowledge back to all clones.
This allowed every clone to correct mistakes simultaneously and continue improving.
Even though the original body didn't directly participate in training,
he could still analyze and refine the incoming data,
saving huge amounts of chakra and time.
This system maximized the advantages of his abilities.
Of course,
only someone like Ren—
who possessed memories from two lifetimes
and the overwhelming mental strength of the Eternal Mangekyō Sharingan—
could handle the immense mental load of such information processing.
If someone else tried this method,
they would probably collapse from mental exhaustion during the first synchronization.
Even Naruto, as the Nine-Tails jinchūriki with the Sage Body and massive chakra,
could only quickly recover physical fatigue.
Mental exhaustion was another matter entirely.
For most people,
traditional training would actually be safer.
But Ren created this system not just to learn ninjutsu and forbidden techniques.
It was also meant to assist him in developing entirely new techniques in the future.
His clones would effectively become research assistants.
"No problem!"
"Leave it to us!"
"Boss, you can just relax!"
The wood clones responded enthusiastically.
They began training according to the Flying Thunder God method.
Starting from the most basic stage—
engraving the teleportation formula with chakra.
Time passed slowly.
Information synchronization occurred again and again.
Progress skyrocketed.
It was even twice as fast as Ren had expected.
Because—
in less than one hour,
the first stage of Flying Thunder God had already been completed.
Flash!
After absorbing the success data sent back by the clones,
Ren's original body vanished instantly.
He appeared beside a spatial marker carved by one of the clones.
"Excellent!"
Ren was delighted.
"Next—start researching the second stage of Flying Thunder God!"
He gave the order.
Previously,
most ninjutsu he learned required almost no effort.
Many techniques he could master immediately after reading them.
So he rarely needed the clone-sharing training system.
Usually he only used clones to study the Uchiha clan archives—
records left by past shinobi who had developed secret or forbidden techniques.
Even so,
the efficiency was incredible.
Over two years,
this process had built a deep foundation for Ren.
But even he had underestimated
how powerful this shared training system truly was.
Inside the inn.
Tsunade returned to her room.
For some reason,
she felt restless.
"Can that brat really do it…?"
Looking at the dark night sky, Tsunade muttered to herself.
"No way. Flying Thunder God isn't an ordinary technique. Only Tobirama, the creator, and Minato have mastered it in Konoha."
"Even if Ren has talent in space–time ninjutsu, there's no way he could learn it that quickly…"
"And after training, he'd probably collapse from exhaustion."
Thinking about that brat's extremely mischievous hands,
Tsunade felt her cheeks heat up slightly.
This wasn't two years ago anymore.
The kid had grown way too quickly.
Inside the room,
Tsunade waited anxiously.
As a teacher,
she hoped Ren would succeed.
Yet at the same time,
she was afraid he might actually win the bet.
She worried that if she spent too much time in close contact with this increasingly handsome and nearly perfect disciple,
she might lose control.
That would be the ultimate humiliation—
an older woman chasing a younger man.
"Phew… five minutes left."
Looking at the clock approaching nine,
Tsunade finally relaxed.
"Looks like he failed."
Suddenly—
Whoosh!
A kunai shot through the window.
Tsunade's eyes narrowed instantly.
She tensed in alert.
But the next moment—
a black figure flashed.
The kunai with the special formula was caught firmly in the man's hand.
"Ren?"
Seeing the familiar smiling face before her,
Tsunade froze.
At some point,
this kid had grown taller than her.
"What was that just now…?"
Tsunade stared at him in shock.
"Flying Thunder God… second stage?!"
Even though she couldn't perform the technique herself,
she understood its mechanics.
Flying Thunder God – First Stage:
Teleporting instantly to a fixed spatial marker.
Flying Thunder God – Second Stage:
Throwing a marked kunai toward the enemy and teleporting to it mid-flight to attack.
The difficulty increased several times over.
Yet Ren had mastered both stages
from scratch
in less than three hours.
It was unbelievable.
"Hehe… don't compare me to normal people, Tsunade-nee."
Ren suddenly lunged forward and hugged her tightly.
His arms wrapped around her soft, full figure.
Looking straight into her beautiful face,
he said eagerly,
"Don't even think about backing out."
Seeing his dazzling smile—
yet also the faint exhaustion on his face—
and the hopeful look in his eyes,
Tsunade felt her heart soften.
She had originally planned to shamelessly refuse the bet.
But now she couldn't bring herself to do it.
Her gaze became gentle.
Pinching his cheek affectionately, she said,
"You brat… when have I ever broken my word?"