Night fell.
At Might Guy's home, Yagyū Souma arrived as promised and planted the curse mark on Guy.
Once you've done it once, the second time is easy.
By now, Souma could implant the curse mark with remarkable ease, keeping the affected blood, chakra, and sealing formulas confined to an extremely small area.
Without careful inspection, it looked like nothing more than a tiny red dot.
Might Guy tested it briefly.
It could indeed absorb and store chakra.
"You're testing it already?" Souma said. "Although it can absorb and store chakra, to actually use this power properly, the Yin Seal has to be completely filled first. That's also the biggest drawback of my curse mark."
"That's already impressive enough," Guy replied with a grin.
At the same time—
"You're not a normal lifeform anyway. Food doesn't really matter to you," the Nine-Tails muttered.
Souma didn't dwell on it.
The Nine-Tails' sensory abilities earlier had caught his attention, but he quickly shifted focus back to himself.
Because—
That diagram…
Wasn't that a Hyūga clan chakra pathway chart?
Souma listened as Kakashi explained his situation, and things clicked into place.
The "gift" for the Yin Seal had been prepared for a long time. Souma had even instructed it earlier to seriously study sealing techniques.
Among jōnin, Kakashi's chakra reserves were neither high nor low—but carrying a constantly draining, high-consumption Sharingan meant his effective chakra pool always looked pitiful.
How many prolonged battles could he really fight?
That… made sense.
The Yin Seal had no rebuttal.
Souma had considered it, but after thinking it through, he felt the Eight Gates didn't mesh well with that technique. Forcing Might Guy or Lee to use Kakashi's style—
And besides…
It was already late. Souma decided to come back the next day.
He let out a helpless sigh.
The core issue with the Yin Seal was—
He stretched slightly.
Souma had taught the Yin Seal Sage Mode. Given how diligently it studied, there should have been progress by now.
"Have you ever entered Sage Mode?" Souma asked.
Kakashi shook his head. "Briefly. About one second. Then I was forced out immediately."
That answer surprised Souma.
The Nine-Tails' split consciousness snorted.
Souma looked at Kakashi. "Bring Sakura and Sasuke along next time. I want to see how Sasuke's been progressing."
Kakashi paused, then nodded.
He knew Souma possessed mental-type techniques, and by putting himself in Souma's position, he vaguely understood the plan.
"Tsunade-sama's Yin Seal for me is indeed like that," Kakashi said. "Mine is an improved version—and it's not limited to the forehead."
"So you're not going?" Souma asked.
Kakashi smiled faintly. "I am."
Souma gestured to his forehead, then to the area near his heart.
"I also developed several smaller chakra storage points. They don't hold much individually, but it's far better than having nothing."
The Nine-Tails jumped out immediately.
"Hey—are you trying to turn the whole body into a battery?!"
Kakashi inhaled sharply.
First thing in view wasn't the Yin Seal itself, but a full-body chakra pathway and tenketsu map—one that even the medical corps didn't possess in full.
Souma had clashed with Akatsuki.
Souma smiled. "Yep."
"Both," he added casually.
Kakashi quickly grasped the overall picture.
Even if not every ninja could form a Yin Seal, following these notes would at least let them achieve thirty percent of the effect.
That alone was revolutionary.
Kakashi stared at the notebook, stunned.
"So… you came because Guy said I hadn't mastered it yet?"
Souma shook his head. "No. I just wanted to check."
Kakashi rubbed his eye and laughed softly. "Planning to stay in Konoha for long? Tonight, how about dinner with Tenten and Kazusa? My treat."
Souma paused, then smiled. "You caused trouble outside, or gained something big?"
"Both," Souma answered honestly.
The Nine-Tails snorted.
"Teacher? You act more like a mad scientist."
Souma ignored it.
"This technique might actually suit you better," Souma continued. "Honestly, I think it's perfect for you."
"Sage chakra?" Kakashi repeated.
Souma nodded. "Yes. Especially for chakra-deficient people."
Kakashi froze.
If he could store that much chakra—
Wouldn't that drastically extend Sage Mode?
This was a godsend for chakra-poor shinobi.
The Nine-Tails actually agreed to help.
That alone shocked Kakashi.
Souma added calmly, "But don't get too excited. With your current condition, you might last… two or three seconds longer at most."
"…That's still incredible," Kakashi said sincerely.
The next day, at Kakashi's usual training ground, Souma found him waiting.
"!!!"
Kakashi stared at the notes in disbelief.
"You applied Yin Seals to all these tenketsu?!"
Souma nodded.
Kakashi took a sharp breath.
This was beyond anything he'd imagined.
Souma looked thoughtful. "I know the problem now. I have another solution."
The Nine-Tails glanced sideways, immediately suspicious.
"Sensei," Souma said, "don't be happy too soon."
Kakashi sighed. "Two reasons. One—my chakra reserves. Two—my eye."
Souma nodded. "Your guess is correct."
The Sharingan wasn't his. That imbalance affected his mental state and chakra regulation.
"Unless you remove it like I did something similar," Souma said carefully, "you'll never truly stabilize Sage Mode."
Kakashi smiled faintly.
"That eye is the last thing they left me. I'm not giving it up."
Souma didn't argue.
"Also," he added, "aside from the forehead, other locations can store Sage Chakra."
Kakashi's eyes widened again.
The difference was clear—
The Yin Seal was a battery that had to be filled and discharged in one go.
Souma's system allowed distributed buffering.
That changed everything.
Souma closed the notebook. "That's all for now."
He glanced at the Nine-Tails. "Kurama, coming?"
"Depends on my mood," it replied lazily.
Kakashi chuckled.
Looking at Souma, he finally said, with genuine emotion—
"Thank you."
Souma waved it off.
"Just don't get too happy yet."
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