It only took half a day for Uzumaki Rin to master the Summoning Technique: Space-Time Ninja Tool Storage.
As a branch of space-time ninjutsu, the summoning technique wasn't particularly difficult. Compared to the Flying Thunder God Technique, it was far easier. Rin had already started learning the Flying Thunder God from Minato Namikaze, yet he still hadn't even reached the beginner stage.
The next day, Rin bought a large number of blank scrolls and went straight to find Kushina Uzumaki to research sealing techniques.
Since these were meant to be portable ninjutsu sealing scrolls, they couldn't be as massive as the Sealing Scroll. That would be far too inconvenient.
After some thought, Rin decided to model them after the "Heaven and Earth Scrolls" used in the Chunin Exams.
Compact, easy to carry, and convenient to use.
Perfect for… everyday use—or eliminating enemies.
After a full week of research with Kushina, they successfully developed a special sealing formula tailored for these scrolls.
From there on, sealing the jutsu itself would depend entirely on Rin.
That day, Rin created hundreds of Shadow Clones—but instead of training, they all carried stacks of scrolls out of the house and began testing.
"...Sigh, another failure."
Rin slumped over the table as a clone dispersed, sending its feedback back to him.
Sealing ninjutsu was far more technical than he expected.
Chakra flow too fast → scroll breaks instantlyToo slow → sealing formula activates before completionToo dense → scroll explodesToo weak → scroll works, but has no power
It required perfect balance.
Right now, he was testing with Earth Style: Earth Wall—a safe option. Even if it failed, at most it would create a wall of dirt.
Still, the courtyard was now filled with uneven dirt mounds and jagged rocks—evidence of countless failed attempts.
At noon, Rin sat eating the lunch prepared by Kurenai Yuhi, but unlike usual, he didn't say a word.
"Rin… is it not tasty today?" Kurenai asked nervously.
He snapped out of his thoughts.
"No, it's great as always. I just ran into a problem and have been thinking about it."
"Oh… I'm sure you'll solve it soon. I believe in you," she said, smiling.
"Of course I will."
He said it confidently—but inside, he had no clue.
Afternoon passed quickly.
Just before dismissal, their Chunin instructor walked in.
"Tomorrow will be your monthly assessment. The tests will include reconnaissance, shuriken throwing, and practical combat. Make sure to prepare—"
Before he could finish—
BANG!
"DAMN IT! After wasting hundreds of scrolls—I finally did it!"
Rin slammed the desk and shot to his feet.
The entire class froze.
Ignoring them, he immediately formed hand seals.
"Summoning Technique: Space-Time Ninja Tool Storage!"
Puff!
A scroll appeared in his hand.
His first successful ninjutsu sealing scroll.
"Uzumaki Rin! Were you even listening?! What are you doing?!"
The teacher completely lost it.
Sleeping in class was one thing—but interrupting him like this and performing summoning jutsu in the classroom?
Enough was enough.
In a fit of anger, he hurled a piece of chalk straight at Rin's forehead.
Killing intent…!
Instinctively reacting, Rin tore open the scroll in his hand.
BOOM!
A massive earth wall erupted inside the classroom, completely blocking the harmless chalk.
…
Oh no.
That was overkill.
Desks shattered. Walls cracked. The ceiling filled with spiderweb fractures.
This was bad.
Very bad.
Without hesitation, Rin used a Body Flicker Technique and vanished before anyone could react.
A few seconds later—
"Uzumaki RinEEE!!! I'M GOING TO KILL YOU!!!"
…
Inside the Hokage's office.
"Lord Hokage, that Uzumaki Rin is absolutely outrageous!" the Chunin teacher complained tearfully.
Hiruzen Sarutobi glanced at the half-destroyed scroll on his desk.
"I understand. You've worked hard. I'll handle it—go back."
"Yes, Lord Hokage…"
After the teacher left, Hiruzen simply sent an Anbu operative to repair the academy building.
Nothing more.
To others, it was a small incident.
But to him…
It revealed something significant.
Ninjutsu sealing scrolls.
This concept wasn't new.
The Tobirama Senju had once explored it.
But even Tobirama failed to develop a method suitable for large-scale use. The process was too complex—production too slow.
So the idea was abandoned.
Yet now, over twenty years later…
Hiruzen was seeing it again.
And this time—
There was a possibility it could be mass-produced.
And that possibility…
Was Uzumaki Rin.