Chapter 3: Fusion! The Eternal Mangekyō Sharingan
Nan could clearly feel the changes in his body—not only had his wounds fully healed, but something deeper was happening.
After absorbing Uchiha Han, all of Han's abilities were gradually being assimilated into Nan's new body and beginning to awaken. Among them was Han's Mangekyō Sharingan.
It was as if Han's eyes had been directly grafted onto Nan's own. This essentially gave Nan access to two sets of Mangekyō abilities, freely interchangeable at will. This discovery thrilled him.
As any die-hard Naruto fan would know, if two direct blood relatives both possess the Mangekyō Sharingan, then transplanting one sibling's eyes into the other allows their ocular powers to merge—thus awakening a new, more powerful dōjutsu: the Eternal Mangekyō Sharingan (EMS).
Having watched Naruto dozens of times, Nan was well-versed in this method of evolving the standard Mangekyō. In fact, no one understood it better than him.
Unlike Uchiha Madara or Sasuke in the original story, Nan hadn't gone blind nor undergone a traditional eye transplant. However, he now truly possessed two Mangekyō Sharingan from blood relatives, meaning he fulfilled all the conditions for awakening the Eternal version.
Its emergence was now only a matter of time—which was exactly why Nan didn't regret using his precious Formless Reincarnation technique to absorb Han.
He believed that with the Eternal Mangekyō, the cooldown of Formless Reincarnation would surely shorten—or even reset entirely due to the power surge. Such an outcome was entirely plausible.
To awaken the Eternal Mangekyō Sharingan, the wielder's chakra had to fully adapt to the new eyes and absorb their power.
In the original series, after transplanting Itachi's eyes, Sasuke needed time to adapt before his Eternal Mangekyō fully awakened. But Nan didn't need that.
Even for siblings, it would typically take months for their chakra to fully synchronize. But thanks to the unique nature of the Formless Reincarnation, which had fused Han's Mangekyō directly into his own, Nan had completely skipped that stage.
As a result, the emergence of his Eternal Mangekyō Sharingan was dramatically accelerated.
Sure enough, once Han's ocular power fully settled into Nan's eyes, he immediately sensed a change.
Had a mirror been in front of him, he would have seen two distinct, yet subtly similar pinwheel patterns alternating rapidly within his crimson Sharingan—one representing Nan's Mangekyō, the other Han's.
Nan understood that this was the sign—the prelude to the Eternal Mangekyō's awakening. And it had come faster than he expected.
The alternating of the two designs grew more rapid, their rotations increasingly fast, until the difference between them became indistinguishable. The fusion was entering its final stage.
Though Nan couldn't see the transformation himself, he could feel it. His eyes now throbbed with a sensation much like the one he'd felt during his initial Mangekyō awakening—only far more profound.
His eyes pulsed like a beating heart. A sharp, aching pressure built up within them.
Suddenly, Nan felt something drip from his eyes. Reaching up to touch, he found twin streams of blood-tears running down his cheeks.
He didn't panic. Having read and watched the original series countless times, he knew that bleeding was a normal side effect of awakening powerful dōjutsu.
The fusion had reached its peak. The discomfort became unbearable, forcing Nan to shut his eyes tightly.
When the pain finally began to subside, and he slowly reopened them, the pinwheel designs in his eyes had stabilized.
The spinning slowed, revealing a new, refined pattern—an elegant windmill design, similar to Nan's original Mangekyō, but now more intricate, infused with subtle elements of Han's.
The fusion was complete.
The Eternal Mangekyō Sharingan was born!
"Whew… finally," Nan exhaled deeply, beginning to sense the changes within his eyes.
"So this is the Eternal Mangekyō… It's definitely different from the ordinary version."
Even without activating any of its abilities, the standard Mangekyō would cause pain upon use. Casting its jutsu only made that agony worse—sharp, piercing, and often unbearable.
But now… things had changed.
Nan could already feel it: the steadiness, the clarity, the overwhelming power—and no trace of pain.
This was just the beginning.
Back when Nan had been fighting Uchiha Han, the pain from activating his Mangekyō Sharingan nearly caused him to pass out. But in a life-or-death moment like that, he could only grit his teeth and endure it.
Now, things were different.
Even though his Mangekyō was clearly active, there wasn't even the slightest trace of pain.
Now, his eyes pulsed with a sense of overflowing power. Rather than draining chakra from his body, he could feel chakra pouring outward from his eyes, strengthening him from within.
"No wonder Itachi's body broke down at such a young age," Nan muttered in realization. "Turns out it wasn't just illness—the standard Mangekyō Sharingan itself was a huge burden."
He finally understood:
The Eternal Mangekyō was different. Not only did it eliminate the debilitating side effects, but over time, it actually fed more and more chakra back into the body.
For the first time, Nan could relax. He no longer had to worry about the Mangekyō stunting his growth or harming his health.
Then came the changes to his Mangekyō's ocular ability.
Just as Nan had hoped, the cooldown time for Formless Reincarnation—a powerful jutsu that once had a 15-year cooldown per eye—was dramatically shortened. Now, it could be used again in just five years.
Five years was still a long time, but Nan was more than satisfied. After all, an ability this powerful being even remotely reusable was already insane. If word got out, other Mangekyō users would probably be so ashamed they'd kill themselves out of inferiority.
What more could he ask for?
Nan even started making future plans:
If he ever had the chance to transplant the First Hokage's cells, he was certain the cooldown time would shrink even further.
In the original series, the power of Hashirama's cells was clearly shown. For example, Danzo used the eye technique Kotoamatsukami to try and control Mifune. Though it failed, not long after he was able to attempt using it again on the masked man posing as Madara.
That proved just how greatly Hashirama's cells boosted ocular recovery.
As already mentioned, using a normal Mangekyō causes extreme strain—even someone like Itachi, a born Uchiha, couldn't endure it.
And Kakashi, who wasn't even an Uchiha, had to rest for long periods after every use of his Sharingan.
Yet Danzo, also lacking Uchiha blood, was able to implant eleven Sharingan (including at least one Mangekyō) thanks to Hashirama's cells—and freely used them in battle. That showed just how absurdly effective those cells were.
Even Obito, who didn't possess the Eternal Mangekyō, was able to wield a regular Mangekyō more effectively than Eternal users thanks to having half of his body made of White Zetsu—essentially a clone infused with Hashirama's DNA.
All of this pointed to one conclusion:
Hashirama's cells might enhance the Mangekyō even more than evolving it into the Eternal form.
"If I can get my hands on those cells someday," Nan thought to himself, "my ocular power will reach unimaginable levels. Even the Rinnegan might be within easy reach."
A plan was quietly taking shape in his heart.
But just then, Nan suddenly felt a strange new sensation from his eyes. He froze, quickly focusing his attention and sensing the change.
"…Ha! I can't believe it—this is incredible!"
Nan burst into laughter.
It turned out Formless Reincarnation had given him yet another surprise.
Carefully sensing his own chakra, Nan realized he could still switch between the two Mangekyō patterns—just as he could before the Eternal Mangekyō awakened.
Han's Mangekyō hadn't been absorbed or erased.
It still existed!