"Ninjutsu should be learned as a system," Kushina said, scratching her head as she thought hard.
"So for the next jutsu… let's go with the upgraded version of Shadow Clone Jutsu—Multiple Shadow Clone Technique."
"Multiple Shadow Clone Technique," she continued. "Although it's an A-rank jutsu, it's really just an enhanced form of Shadow Clone Jutsu. The difficulty of learning it shouldn't be too high."
Hagoromo glanced at Kushina in silence.
The learning difficulty isn't high, sure—but this is a forbidden jutsu, he thought. It consumes absurd amounts of chakra, alright?
Besides, given his fighting style and physical constitution, ordinary Shadow Clone Jutsu was already more than sufficient. There was basically no scenario where he'd need Multiple Shadow Clone Technique.
Still, since Kushina was willing to teach it, he would learn it properly. As long as he strictly controlled the chakra output, the risks of the jutsu could be avoided.
The danger of Multiple Shadow Clone Technique lay in the need to distribute a massive amount of chakra all at once. Poor control could result in serious injury to the user—but Hagoromo was confident that his chakra control was more than adequate.
Even so, he added cautiously,
"Um… Kushina-sensei, Multiple Shadow Clone Technique is a forbidden jutsu, right? Is it really okay to teach it to me?"
"It is forbidden," Kushina admitted, "but since I'm teaching you, do you really think the Third Hokage would object?"
Hagoromo desperately wanted to say:
Kushina-sensei, you're misunderstanding me. I'm not asking whether the Hokage approves. I'm asking whether this jutsu is going to get me killed.
Fortunately, Kushina continued explaining.
"Although it's classified as a forbidden jutsu, the restriction mainly applies to ninja below jōnin level. For jōnin, it's not a big deal. Based on my sensing, your chakra reserves are… passable. So it should be fine."
"…Probably."
Hey—what do you mean probably?!
So there's still a risk after all?!
The difference between Shadow Clone Jutsu and Multiple Shadow Clone Technique lay in the amount of chakra flowing through the chakra network.
If Shadow Clone Jutsu required a chakra output of 1, then creating three clones would require 3 units of chakra to flow through the same pathways simultaneously.
That was easy enough to understand.
As long as the number of clones stayed in the single digits, the difficulty and danger remained manageable.
But if one tried to create more than ten clones, the difficulty skyrocketed.
Hundreds? Thousands?
Only freaks of nature like the Uzumaki Clan or the Senju Clan could pull that off.
Hagoromo didn't even bother dreaming about it. His chakra reserves were excellent by ordinary standards—but compared to Uzumaki monsters, he'd only end up quietly injuring himself.
"Watch closely," Kushina said, demonstrating the jutsu once more.
Hagoromo was someone who understood trade-offs very well. When practicing Multiple Shadow Clone Technique, he never created more than five clones at once. Under such controlled conditions, he successfully grasped the jutsu.
"Very good. You're remarkably calm about this," Kushina said, patting his shoulder.
"Alright then—one more jutsu today. This will be the last one for today. It's still part of the clone-jutsu system: Shuriken Shadow Clone Jutsu."
Hagoromo couldn't help but wonder—
Isn't this jutsu basically copyrighted by the Third Hokage? Are we really allowed to be this blatant?
In fact, that would be a problem—for most people.
For Uzumaki Kushina, however, it wasn't a problem at all.
To be honest, Kushina was feeling a bit uneasy herself—but not because of infringing on the Third Hokage's intellectual property.
What made her uneasy was Hagoromo's learning speed.
If she didn't pace herself, wouldn't all the jutsus she knew be learned by her student in no time? What would she teach him then?
That would be tragic.
Landing a student like this wasn't just fortunate—it was borderline disastrous.
Still, she thought of how Minato constantly praised Hatake Kakashi.
Hmph.
Gritting her teeth, she continued teaching Hagoromo.
As for Hagoromo, he was already more than satisfied.
Aside from Kushina, what other teacher would casually teach him three high-level jutsus per day?
Of course, with his current chakra reserves, he couldn't freely unleash multiple high-level jutsu in actual combat. Still, his curiosity made it impossible for him to resist the allure of advanced jutsus.
The more advanced a jutsu was, the more mysterious it became—and the more irresistible it was to him.
Thus, Kushina trained Hagoromo while handling her own duties. Occasionally, due to pressure from the Hokage and constant persuasion, she even took Hagoromo along to do low-level missions like catching runaway cats or chasing dogs.
Time flew by.
Before he realized it, three months had passed since Hagoromo graduated from the Ninja Academy.
All of his peers had long since followed their squad leaders to the battlefield. Hagoromo even suspected that many of them had already fallen in battle.
Yet he himself hadn't taken a single step outside Konoha's gates.
From this perspective, he had unknowingly fulfilled his role as a "toy" perfectly.
"…Huh?"
"Kushina-sensei, you seem unusually cheerful today," Hagoromo said, looking at her.
"You don't look nearly as troubled as you did before."
In truth, Kushina had been irritable for days due to stalled progress in ninjutsu development. Her sudden good mood today was genuinely strange.
After three months together, Hagoromo understood Kushina's personality quite well.
"Did something change with the development of the Four Symbols Seal?" he asked.
That's right.
Over these three months, Hagoromo had evolved from a complete novice into a professional assistant capable of aiding in S-rank forbidden jutsu development.
Kushina handled the design of the sealing formulas.
Hagoromo handled the calculations and structural analysis.
Their cooperation was surprisingly smooth.
The Reaper-style Four Symbols (Dead Demon Consuming Seal)—known as the Reverse Four Symbols Seal—was an extreme mutation of the standard Four Symbols Seal. It was an S-rank research task issued by Konoha's sealing research division.
Originally, this jutsu was designed as a suicidal move: when a ninja was on the verge of death, activating it would seal both themselves and all surrounding enemies.
However, Hagoromo proposed a different idea.
He believed that limiting the jutsu to human use drastically reduced its potential. If it could be transferred onto sealing scrolls instead of the human body, it could become an extraordinarily aggressive offensive fūinjutsu.
Kushina found her student's idea fascinating—and felt that the original task requirements severely underestimated her abilities.
So she chose to modify the jutsu according to Hagoromo's proposal.
Only after truly beginning the work did they realize just how terrifyingly difficult this jutsu was.
As a result, Hagoromo found himself frequently facing a near-berserk Kushina.