I know I already have fic currently running but I absolutely could not get this idea out of my head. This fic features an Au where the Eternal Mangekyo Sharingan works just a bit differently and the consequences this brings. Also I don't know how much I changed the events leading up to Madara getting the EMS but whatever.
I should also note that I wrote this first chapter in a certain style that is not going to stick around. Think of this more like a prologue, the rest of the fic will feature more traditional writing.
I do not own Naruto, obviously.
"Nii- *cough* *cough* Nii-san, don't be too sad for me now, you hear." Izuna Uchiha consoled his older brother even as a trail of blood made its way down his lips.
Madara Uchiha could have been carved from stone at this moment. The only thing showing he wasn't was the faint trembling of his clenched fist. A small gesture, but one which conveyed both burning rage and deep sadness.
Madara simply sat over his brother, saying nothing. What more was there to say? To Madara his sibling was but a blur of color lying upon the battlefield of their clan's latest skirmish with the damnable Senju. A battlefield where Madara and his brother were once again forced to use their evolved eyes to repel their hated foes, wasting even more of their precious eyesight. Never would the two heirs to the Sharingan have thought that their eyesight of all things would have been an expendable resource requiring close management but here they were; two dying brothers, one literal and the other metaphorical, both unable to see the sadness conveyed within the other's ever dimming eyes.
Izuna smiled, or at least Madara thought he did. It was so like Izuna to smile even as he bled out from the gaping hole in his chest. The ground around the two blurred red, and a heavy metallic scent filled the air. Madara was not proficient in medical ninjutsu, no Uchiha were, but he was proficient in the art of killing and he knew with acute clarity that this was too much for even the most skilled healers of the Senju to fix.
*Cough* More blood trailed down. "Nii-san come closer, why don't you? I'd like to see your face one last time." Madara obliged even as the mention of his impending death ripped at his heart more than any enemy kunai ever had.
"Ahh still have that stoic face on, good, I thought you had changed for a second there." Whether Izuna was trying to distract himself or him, Madara didn't know. All Madara could think of at the moment was how he still couldn't see the face of his brother even from this close up. He frowned slightly, his heart sinking even further down than it had already.
His frown was ever so slight but Izuna still caught it, there were times where he was much more observant than he appeared *Cough cough* "Ni-san your eyesight has deteriorated this much? Damnit! I told you to stop fighting my battles, what are you going to do now?"
"..." Madara said nothing even as the trembling in his fists increased. It was so like Izuna to fuss over him even with one foot in the grave.
*Cough cough COUGH!* Izuna turned his head as a large clump of blood came out of his mouth. His breathing turned shallower. Madara was no professional sensor but even he could feel his constantly dimming chakra take a nosedive.
No! It was too soon! It was no longer just his fists which were trembling but his whole body.
"Pr-promise me nii-san." Izuna started, his final request. Madara focused on him, the constant awareness he maintained on their surroundings fell away. It was a moment in time where only the two of them existed.
"My eyes, take them!." Madara's eyes widened in unconcealed shock. "I'm ..going to be with mother now." Tears began to mix with the blood on the ground. "And I...don't want to see your face...for...a...long...time...you hear me…. He trailed off, his spiritual chakra dissipated, his body grew cold, their fellow clansmen came to bring them both back, and through it all Madara couldn't see a thing.
"Run! He's a monster! Retreat!" Shouted the group of Senju who were overconfident enough to have attacked him, foolishly believing that numbers could make up the difference between their skill.
Madara coldly smiled as his eyes took on a form never before seen among the Uchiha. He had since dubbed it the Eternal Mangekyo Sharingan because it was able to continuously use its Mangekyou abilities with no cost to the user's vision. The first time Izuna's pattern bled into his own, Madara was nothing short of speechless; to think the Sharingan held such potential!
Through extensive searching of the clan library Madara had found an instant where a Mangekyo user had taken another's eyes to maintain his combat effectiveness, yet nothing like this had happened. He then proceeded to study it as much as he was able to with his clan's mediocre medical ninjutsu knowledge and the difficulty inherent in studying his own eyes. His conclusions were thus: the EMS was formed by combining two Sharingans of closely related family which possess the Mangekyo. This leads to the patterns combining and the cessation of vision loss as well as a marked increase in the eyes power.
Satisfied with his discoveries so far, Madara recorded the information on the Uchiha's secret records, reserved for future clan heads. He had no desire to spread the information around the compound as there was already a major problem among the clan; every once in a while someone would go and kill their best friend in hopes of gaining the Mangekyo and increasing their power. It was a horrible thing but in times of constant war like this, such a thing was more tempting than one would think. It was exactly for this reason that his ancestors kept things such as Izanami and Izanagi under wraps as it had almost led to the extinction of the clan when one group of radicals began harvesting their fellow clansmen like cattle for their eyes.
Madara was not one to make the same mistakes his ancestors had and thus the secret of the Eternal Mangekyo Sharingan and its method of attainment would remain a closely guarded one, only known by the clan head and the heir apparent. This in turn led to Madara himself being the only EMS user to appear among the Uchiha. A title which was soon to be broken by a certain avenger.
Little was Madara aware though that this would result in something that would shake the shinobi world to its core. This is because Madara was unknowingly mistaken in his findings. One little known fact about Izuna and Madara Uchiha was that they shared the same Mangekyo ability in both of their respective eyes. This fact resulted in Madara misunderstanding a fundamental aspect of the EMS; it is only in the case that both Mangekyo abilities are the same that it will remove the vision penalty inherent within the form. After all, the EMS is a combination of both Sharingan so it makes sense that when they are the same it results in the ability being strengthened as well as its deficits being removed, but in the case that the abilities differ… Well the results are much more variable, as one Sasuke Uchiha is about to find out.
At the moment Sasuke was in what any sensible person might call a bout of psychopathy. Not that any would be observer could blame him too much for this. He had just recently found out with the death of his brother that the life he had been living up to that point was nothing more than a lie. That the man he hated more than anything had in fact loved him more than anyone and the man who had truly orchestrated the death of his family had gone unpunished for years.
So as any self proclaimed avenger would, he avenged. That foul excuse for a human being Danzo was dead but not before going through countless of his clansmen's eyes, almost as if the man had intended to deliver a final "fuck you" to the Uchiha. This compounded with the fact that he had to integrate his brother's eyes into his or risk blindness as a teen who valued the strength of his eyes more than any other aspect, well he should be given at least a little slack for not being in the most sound of mental states.
So forgive him for wanting to lash out a bit, especially against a creature as inhuman as that Zetsu thing Madara keeps around him. With a flash, the white humanoid was impaled along the sword of his Susano'o. The creature's screams of pain were ignored as Sasuke pondered his current self. He had just woken up from his surgery and he could feel that his (no, not just his but Itachi's as well!) Sharingan was different. Even under the bandages both eyes felt stronger, sharper, and healthier. For the past few weeks his eyes had always ached from the strain he had put under them even when his Sharingan was deactivated but now the pain was gone.
With a flourish he ripped off the bandaged obstructing his eyes and morphed his eyes into their eternal state. The manic smile that was growing on his face quickly changed into one of fury and confusion. His vision was lopsided! The left eye containing the inextinguishable black flame Amaterasu had perfect clarity while the right containing the ability Kagatsuchi, which allowed him to shape the black flames, was just as bad as it had been before. Had Madara lied to him?
His face took on an unwilling expression, he refused to believe that his right eye would be blinded forever, after all the left one was just fine! Something had to have gone wrong, but yet he could feel that his right eye had evolved as well. Quickly shifting his gaze to the pinned Zetsu he resolved to test it out. Maybe once he used it he would be able to find the problem.
Instantly, the white monstrosity was bathed in black flames. Taking a deep breath to calm the apprehension in his heart, Sasuke activated Kagatsuchi and took control of the flames. What?! Sasuke's heart dropped as the vision in his right eye turned completely black, he didn't know how to explain it but he could feel in his heart that he had just gone blind in that eye. NO!
He suddenly felt a burning pain that almost seemed to originate from his soul. At this, his attention quickly turned to the Zetsu and he bore witness to a horrifying sight. The flames of Amaterasu had turned a vibrant red, the exact shade as the Sharingan but that was not all. The flames were traveling up the manifested sword of his Susano'o that had pinned the Zetsu down. Almost instinctively, Sasuke made to put them out but he was met with a problem. The thing that allowed him to freely extinguish Amaterasu was Kagatsuchi but now that was no longer an option for obvious reasons.
He tsk'ed as he was forced to deactivate his Susano'o but his face soon changed to one of horror. The red flames had previously been slowly moving up the purple sword but now they moved across the rapidly disappearing Susano'o at a speed which not even Sasuke's Sharingan could track!
Before Sasuke could even think of disappearing from the spot in a kawarimi he was engulfed in red flames. He couldn't help but let out an agonized scream at the pain that consumed him. He didn't even feel himself start to fall as he lost consciousness. His only coherent thought being to wonder if this was it. Was this how the great Sasuke Uchiha would go, killed by his own technique?
If any theoretical outsider were to be watching these events unfold they would no doubt notice several details that young Sasuke had missed in the hectic events that followed his use of Kagatsuchi. They would see the black flames engulfing the White Zetsu turn red but instead of acting how any normal fire would, it looked as if someone had taken a photo negative black and white picture of the plant creature. Similarly odd was how the flame didn't actually burn it; it almost appeared as if the Zetsu had simply melted into nothingness leaving nary a trace that it had been there at all. This was much the same for Sasuke himself, the red flames covered him before he hit the ground, changing his color scheme and dissolving him away as if Sasuke Uchiha had never existed in that space. The only thing that would let a newcomer know that something had occurred here was the continuously burning red flame that remained even as it ran out of fuel to consume, ominously burning in the air in a vaguely human shape.
The problem with assuming anything in the shinobi world is that one should never assume in the first place. In a world where alien rabbits are sealed in the moon and gigantic monsters made of pure energy are stored in children. assumptions are insufficient, one must know. Take Madara for instance, he assumed that all Eternal Mangekyo Sharingans would be like his, but that is simply not true. Two Mangekyo Sharingans, Tsukuyomi, a time manipulating genjutsu and Kagatsuchi, a doujutsu able to control black flames were combined on that day. It would have probably been fine had their later aspects merged but regrettably for everyone, and Sasuke in particular, it was the former.