The next evening.
"Kushina-sensei, I'm going to start carving the seal," Hagoromo said.
In a room on the second floor, besides Kushina, only he and Minato were present. The youth was about to carve the final part of his sealing barrier onto his teacher's back.
"Begin," she said.
Since she had accepted his reasoning, she no longer dwelled on it. The sealing formula was pitched as a last resort to prevent the Tailed Beast from escaping. In her mind, if the situation actually deteriorated to the point where this jutsu needed to be activated, her fate would already be sealed.
"It's merely a preventative measure. That sort of thing won't happen," Minato said from the side. His expression remained warm, but under these circumstances, he couldn't help but worry.
"Then I will begin."
Hagoromo nodded at Minato and started carving the jutsu formula.
Mutually Multiplying Complex Four Symbols Seal—this was the name of the sealing barrier he had set up.
And the key to activate this barrier was about to be placed on Kushina.
It was simultaneously the activation key and, practically speaking, the only safety measure provided after the jutsu's activation. After all, this jutsu was never truly meant to deal with the Tailed Beast.
The underlying principle was simple; it was essentially just a modification of the Four Symbols Seal.
Whether it was the Four Symbols Seal or the Reverse Four Symbols Seal, they were both inward-collapsing seals. Their primary function was to restrict, or even obliterate, a specific space with an absolute contracting force. To put it in perspective, this contraction was like using a terrifying gravitational pull to suck in and lock everything within a designated area.
The jutsu formula being carved onto Kushina had a standard Reverse Four Symbols Seal on the outermost perimeter, while the interior consisted of a different kind of Four Symbols Seal.
After complex conversions and countless experiments, Hagoromo had successfully inverted the Four Symbols Seal, transforming that "gravity" into "repulsion." This was used to offset part of the Reverse Four Symbols Seal's destructive effect, isolating her from the danger.
In terms of the formula itself, the entire sealing jutsu consisted of two parts: a smaller portion on her body, and a much larger array etched into the external environment. Structurally, however, the jutsu as a whole was composed of three distinct sections.
To put it bluntly, this entire setup merely created a safe zone inside the Reverse Four Symbols Seal. Outside the safe zone, the Reverse Four Symbols Seal would function normally, obliterating everything, while the inside remained completely unaffected.
Through these layered measures, it ensured that once the jutsu activated, Kushina, sitting at the epicenter, would remain perfectly unharmed.
When the sealing barrier activated, the outer wall of the Reverse Four Symbols would expand on the perimeter, while she would remain in the isolated safe space within.
A perfectly safe, isolated space.
The Reverse Four Symbols Seal on the outside, the safe space on the inside. As for the middle section, it functioned as the engine that would sustain the barrier.
Normally, a Reverse Four Symbols Seal only lasts for a brief instant from activation to completion, but this modified jutsu would persist for over ten minutes. Therefore, only a massive chakra reserve like Kushina's could power such a demanding technique.
Moreover, compared to a standard Reverse Four Symbols Seal, the scale of this jutsu was completely different.
Assuming she was accidentally taken away from this location due to some mishap, relying solely on the formula on her body, the barrier space opened would be the same size as a standard Four Symbols Seal. But if she remained here, leveraging the massive jutsu formula Hagoromo had prepared in the surrounding area combined with her chakra, the space could instantly expand to a three-kilometer radius.
Going even deeper, if the array extracted the Nine-Tails' chakra to fuel itself, the scale would explosively increase to over ten kilometers.
Once this jutsu activated, everything within that massive range—except Kushina—would be obliterated into nothingness. That was why Hagoromo likened it to a Nationwide Transmutation Circle.
This ultra-long duration and potentially limit-breaking scale, boasting terrifying efficacy, was actually designed to counter just one single jutsu:
Kamui.
The method and logic weren't delicate, but simple and crude was equally effective. Hagoromo couldn't remember exactly how long the right eye Kamui's intangibility could last, but ten minutes should definitely be enough to outlast it.
He focused intently on his work. In just a short while, the jutsu formula covered Kushina's entire back, leaving almost no bare skin visible.
However, at that moment, Minato grabbed Hagoromo's hand, forcing his work to come to a sudden halt.
Minato had ample reason to stop him, because the jutsu formula Hagoromo was drawing was not the same as the one he had shown them beforehand.
The alteration was minimal, but Minato spotted it at a glance.
In the original formula, this sealing barrier could only be activated by Kushina. The timing and the decision of whether to activate it were entirely up to her. But now, she wasn't the only one who could trigger it; there was a second person.
This second person was naturally Hagoromo himself.
With this modification, Hagoromo could remotely activate the jutsu on her body when necessary. The jutsu would then interact with her Eight Trigrams Seal to forcibly extract the Nine-Tails' chakra, maximizing the scale and locking down the entire space.
In that fleeting moment, Minato realized the truth. This jutsu formula wasn't meant to deal with the Nine-Tails breaking out of its seal at all. No wonder it included a mechanism to utilize the beast's chakra.
This jutsu formula was a trap meant to deal with an unknown enemy who might take advantage of childbirth to steal the Tailed Beast.
The reason Hagoromo placed the formula on Kushina's back was twofold: first, the formula was indeed complex, but second, he didn't want her to see the alterations within it. If Minato could see the change, she obviously could too, so Hagoromo deliberately kept it out of her line of sight.
However, if Hagoromo forcibly activated such a jutsu himself, given its immense complexity, it would instantly exhaust his chakra. In a zone of absolute destruction of that scale, without any chakra left, how was he supposed to escape?
Hagoromo turned his head, looking at the Hokage with his usual calm gaze, and then gave a firm nod.
"Are you done yet?" Kushina asked, sensing that the brushstrokes had stopped.
Minato, ultimately, let go of the boy's hand.
"Not yet, but almost," Hagoromo replied, his voice betraying no emotion.
"Then why did you stop?"
"Well... I was looking at the cherry blossoms. Kushina-sensei, if you look straight out the window, you can see them."
"Oh, summer is almost here. These must be the last cherry blossoms of the year..."
"Wait, is this really the time to be admiring cherry blossoms?" Kushina sighed, feeling that with such an unreliable disciple, she was going to catch a cold sitting there half-dressed.
Viewed from this angle, the cherry blossoms bathed in the setting sun carried a bizarre, blood-red hue. But human blood could dye them even redder.
This blood could belong to the enemy, or, of course, to Hagoromo himself.
But ultimately, this was a last resort. He hoped it would never see the light of day. More accurately, long before resorting to this sacrificial method, he and Minato should have already taken care of whatever enemy dared to show their face.
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