Kakashi's Sharingan was, indeed, perpetually active in its three-tomoe state. Closing his eye did absolutely nothing to change that. Objectively speaking, activating the Sharingan was a battle-ready state, inevitably leading to a significant drain of chakra. Even Uchiha clan members wouldn't do this casually. Kakashi covering his left eye with his forehead protector was probably a subconscious attempt to "plug the hole," but this kind of "physical blockage" was utterly useless.
For Kushina, however, using a sealing jutsu to cut off the chakra supply to a specific part of the body wasn't difficult. Even cutting off the chakra supply to the eye...it just required a bit more precision.
The essence of such a sealing jutsu was no different from Habara's own Six-Direction Sealing. The seal would simply remain closed normally, and when Kakashi actually needed to use his Sharingan, he could open the seal. It could even have an added "valve" function to regulate the amount of chakra flowing to the eye.
After listening to Habara's explanation of Kakashi's problem, Kushina immediately took it seriously. No wonder she always felt that Kakashi, who should have been in a "ballooning" stage of power growth, had shown such stagnant progress. Turns out, he'd been leaking the whole time.
As for why Kakashi had never actively brought up his issue with Kushina, it was because he hadn't previously considered it a big deal. After the deaths of his teammates, especially after failing to protect Rin and even causing her death, it might be an exaggeration to say Kakashi had given up on himself, but he was certainly letting himself drift.
Now, Kakashi's experiences were slightly better than his original timeline. At least Kushina was still alive, meaning Kakashi still had a guardian who cared about him.
"Kakashi, let me see your Sharingan. I'll take a look."
Kakashi might have an eye problem, but his brain was fine. He could at least tell who cared about him and who didn't. For instance, Kushina was genuinely worried about him in this room. But why Habara had suddenly dragged him here was a matter worth pondering.
He had a deep suspicion. Why would Habara, someone not even from Konoha, have such a thorough understanding of the Sharingan? It defied logic.
With all sorts of jumbled thoughts running through his head, Kakashi pushed aside the forehead protector covering his left eye.
Kushina looked intently at Kakashi's Sharingan. Then, she extended her right hand, her palm stopping about two or three centimeters from his eye... She seemed to be using her own chakra to probe the condition of his eye.
She maintained this posture for a full five minutes.
Even though Kushina held a highly respected position in Konoha, and might even be able to rummage through the "Book of Seals" at the Third Hokage's place to study, there were things that could be done and things that couldn't. Unquestionably, this was her first close encounter with the Sharingan...her first encounter in a non-hostile situation.
After five minutes, Kushina finally withdrew her hand. "Normally, there wouldn't be so many chakra pathways in a human eye," she said. "But the Sharingan is different. It's filled with a dense network of fine chakra pathways, and..."
She seemed puzzled, but she didn't voice her confusion.
"Anyway, cutting off the chakra supply to the Sharingan isn't difficult. We can even try it right now."
With that, Kushina grabbed a dip pen from the table behind her. She then pulled Kakashi's forehead protector up and his mask down, and proceeded to "scribble" around his eye with the pen.
Habara found the scene somewhat amusing. This was the first time in his life he'd seen what Kakashi looked like. Yep, he definitely has a 'beauty mark' near his mouth. Habara wasn't laughing at Kakashi's appearance, of course. He just thought that despite Kakashi's usual "mysterious" persona, that mystery had been easily stripped away.
It was like those kids who always try to act cool. If their mom wants to pull down their pants, she'll just do it. Who cares about the kid's pride?
After drawing the seal formula, Kushina channeled her chakra into it. She used a gentle, gradual approach, slowly closing the seal and cutting off the chakra supply to the Sharingan. When the seal was halfway closed, and she estimated the chakra supply was reduced to half, Kakashi's three-tomoe Sharingan began to slowly deactivate. By the time she completely cut off the chakra, the three tomoe had vanished, revealing his black iris again.
Now both of Kakashi's eyes were black. If it weren't for the slight difference in shade between the two, his left eye would look completely normal.
"Kakashi, how do you feel?" Kushina asked.
Kakashi blinked, shook his head, and carefully assessed the situation. "For some reason, I feel like my head is clearer," he finally said.
He didn't mention how his eye felt, but rather how his head felt.
Compared to before, Kakashi felt clear-headed and sharp-witted. His previous state felt like his thoughts were shrouded in a hazy, muddled fog.
Not only did the Sharingan "leak" chakra, but it even seemed to put pressure on the optic nerve. Kakashi hadn't noticed it before, but once that sensation was removed, the difference was quite noticeable.
Habara nodded silently. So the Sharingan really does lower your intelligence.
"See? I told you it wouldn't be difficult. Now we just need to design a proper opening and closing mechanism for the seal," Kushina said.
The seal on Kakashi's eye now was obviously temporary, probably lasting only until he washed his face. A permanent seal would be much more intricate.
"The secret of the Sharingan probably lies in the fact that it's born with a certain built-in formula. When chakra is channeled into the eye, the formula is activated, and the Sharingan gains its unparalleled visual prowess... Unfortunately, this formula seems impossible to decipher," Kushina added.
Formula? Hearing Kushina say that, Habara suspected that the Sharingan's formula might originate from the God Tree, given the bloodline connection. But Kushina was wrong about one thing. The activation of the Sharingan's formula didn't just enhance visual prowess. That so-called dojutsu...
Well, it felt like only the Mangekyo and above could be considered true dojutsu.
Kushina looked at Habara, then at Kakashi, whose "clever brain had reasserted itself." She continued, "The eyes of dojutsu clans all seem to have structures that can accommodate chakra. But I feel like the Sharingan's chakra throughput is greater than the Byakugan's. This is a bit strange, because theoretically, the Sharingan shouldn't need that much chakra."
Chakra throughput? Habara thought he understood why members of the Hyuga clan always looked like they were straining, their faces bulging with veins, when using the Byakugan. They were probably "physically pressurizing" it. Perhaps they were expanding the delicate pathways within the Byakugan, or maybe stuffing more chakra into those capillary networks...
Wait a minute!
Had Kushina just said the Sharingan's chakra throughput was high? Habara was suddenly struck by inspiration. No, that wasn't right. The Sharingan's chakra throughput was actually still insufficient... When Uchiha used powerful dojutsu, the Sharingan still lacked "bandwidth," which is why it led to various problems, including blindness.
The Mangekyo Sharingan's dojutsu consumed even more chakra!
Habara felt like he was grasping something. He decided to use a more relatable analogy.
"The Sharingan's formula, or rather, the Sharingan's dojutsu, shouldn't be limited to just enhanced visual prowess. Because some Uchiha have powerful space-time ninjutsu stored within their Sharingan..."
As soon as he said that, Kushina immediately understood, because she had seen "Uchiha Madara."
"Considering the amount of chakra required for space-time ninjutsu, is it possible...that the chakra throughput of an ordinary Sharingan isn't too high, but rather too low?
For example, if someone is chronically constipated, and the, uh, matter has hardened, it gets blocked. The, um...end of the rectum has limited throughput, insufficient diameter. And if you try to force that matter out, it might cause tearing and bleeding."
Was the enlargement and deformation of the tomoe a visual representation of increasing the eye's "bandwidth"?
Okay, this analogy was a bit too relatable, equating the Sharingan to a sphincter. But Habara seemed to be onto something. Why did some people bleed from their eyes after using Mangekyo dojutsu?
Because they had anal fissures!
"Kushina-sama?"
Hearing Habara's explanation, Kushina fell into deep thought. Habara was eager to hear her opinion.
"Ah, now that you mention it, I think little Naruto's diet has been a bit too dry lately. That doesn't seem good for his health, does it?" Kushina looked up and said.
Habara: "..."
No wonder she and Minato were a couple. Her ability to go off on a tangent was unparalleled.
But what about Kakashi? Could anyone understand how he was feeling right now? He felt like his left eye was incredibly unsanitary, and a little itchy.
So, the question was, how to increase the strength of the sphincter... no, how to increase the Sharingan's chakra "bandwidth"?
Habara suddenly looked up. He actually knew how to do it. One way was "parallel connection," transplanting two Sharingan from the same source together. Another way was to increase the organ's vitality and widen the network of pathways within the Sharingan, i.e., using Wood Release cells.
He immediately spoke up, "Kakashi, stay right here. I'll be right back... There's something very much worth trying, and you absolutely must try it!"
With that, Habara left. Less than two minutes later, he returned with Tenzo.
"Kushina-sama, could you design a simple seal with a chakra storage function?" Habara asked.
Kushina nodded. "That's not difficult."
Although no one knew what Habara was up to, everyone could see he was a bit excited, because he was already directing his superior.
"And Tenzo, you need to fill Kushina-sama's seal with your Wood Release chakra. Remember, Wood Release chakra."
Tenzo also nodded.
If Kushina and Tenzo were simply being bossed around by Habara, then Kakashi was now a mere puppet.
Kushina removed the chakra-blocking seal from Kakashi's eye, and the Sharingan immediately returned to its three-tomoe state. Then she redrew a new seal... This small seal wasn't dangerous; it essentially just physically soaked the Sharingan in Wood Release chakra, similar to being soaked in formaldehyde.
"Kakashi, how do you feel?" Habara asked after the seal was completed.
"I feel a strange life force. It feels like grass is about to grow in my eye," Kakashi said.
Habara nodded. This proved that the "catalyst" was working. He then said to Kakashi, "Now, try concentrating chakra into your Sharingan."
"Concentrating chakra?" Kakashi gave Habara a bewildered look.
"Yes, and I'll remind you, when you concentrate chakra, don't look at anyone... Look at the wall, just look at the wall."
"I understand."
Kakashi nodded and began to concentrate chakra into his Sharingan.
"It's a little difficult."
"Don't feel any pressure. Even if you focus all your chakra on your eye, it'll be fine. Trust your sphincter! Try to find that constipated feeling. If that doesn't work, try to find the feeling of childbirth."
Kakashi: "..."
Kushina: "..."
Kakashi took a deep breath. He didn't know what Habara was doing, but he knew that if he didn't go along with it, this probably wouldn't end.
"Alright, I know what to do."
Kakashi focused his mind and instantly channeled most of his chakra into his left eye.
At that moment, the three tomoe in the Sharingan suddenly began to rotate slowly, transforming into the shape of three-bladed shuriken! In an instant, Kakashi felt something immense being released from his Sharingan. Simultaneously, the wall at the focal point of his gaze was instantly twisted, and then, with a "boom," the bricks and stone exploded.
"This..."
Kakashi stood up, feeling a sense of disbelief. However, this single action had not only consumed most of his chakra, but also completely drained Tenzo's chakra. He felt an indescribable pain surge from his eye socket.
He instinctively reached up to cover his left eye and felt a handful of blood.
At that moment, Kakashi suddenly understood Habara's analogy. He really did feel like he had "anal fissures."
Just a few seconds later, the Sharingan returned to its original three-tomoe form. Kakashi simply gave Habara a resentful look, then let out a "gah" and passed out.
This kind of dojutsu was simply too much of a burden for Kakashi at this point.
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