i know that the first paragraph might anger some people, but if it does make you angry then just keep reading! I can almost guarantee that you will not be quite so mad at me by the end of this chapter. And if you are still mad at me by the end of this chapter....there's nothing i can do about it.
congratulations to kk the prophet for figuring out half of the answer, they got the event and circumstances correct but the true reason was a little more.... complicated than just an event. the reasons go deeper than most people tend to go. read on if you want to find out why itachi got the mangekyo sharingan as well as my reasoning as to exactly how i think the sharingan works. and yes i know that certain things in canon may make my reasoning false but this is a fanfic for a reason and as such it is not canon and i do not own naruto.
Itachi sighed as he finished unpacking the last of his belongings, he had been disowned by his clan after they found out that he had fought Fugaku in order to protect Naruto. Oh well, at least he was away from the arrogance of the idiotic Uchiha clan and their false sense of superiority. Of course being disowned technically meant that he could no longer go by the name Uchiha, but he didn't care, too much arrogance and pride was wrapped up in that name for him to continue using it. His only regret was that he would no longer be able to see Sasuke on a regular basis, and no doubt his scheming and conniving uncle (who had replaced the still comatose Fugaku as clan head) would poison Sasuke's mind against his brother. At least the Hyuga clan had agreed to help him out for the time being, even going so far as to grant him a small house on the outskirts of their compound as a thank you for saving the wife and daughter of their clan head. Itachi sighed for what seemed like the hundredth time that day, there was no way that he could continue on as an Uchiha, thus he would need a new name... he would no longer be Itachi Uchiha, from this day forth he would be known as Itachi Mamoru. Yes that had a nice ring to it, and what better way to state his new purpose in life than with his new clan name? After all his entire reason for existence is now to defend Konoha and it's allies, as it should have been all along, so his new name should reflect that (mamoru literally means defend). 'And now to see the Hokage to figure out exactly why my sharingan mutated, there are no recorded instances of this ever happening to another sharingan user. Perhaps he will have a theory once I explain the entire situation to him.' Itachi thought as he headed out the door. The Hokage was certainly in for an interesting afternoon.
The Hokage was just finishing up some paperwork when Itachi knocked on his door, he looked up and smiled, already knowing who it was. "Come in Itachi, I've been expecting you."
Itachi opened the door looking puzzled. "How did you know I would come here Hokage-sama?" he asked, "I only just now decided to come see you."
the old Hokage smiled. "I've been waiting for you to come here since I heard of your clan's actions concerning your defense of Naruto and his family. When you get to be as old as I am you tend to learn how to predict what people will do in any given situation, that foresight is what has kept me alive and in power for so many years. Though I fear I won't be able to do this much longer. Now, what is it that you wanted to discuss with me? Would it be a legal emancipation from your clan perhaps?"
Itachi was surprised, that was exactly what he wanted, but there was more to it than that. Itachi cleared his throat before speaking. "You are correct Hokage-sama, I do wish for a legal emancipation from my clan, but that is not all that I need. I also wish your council in a matter of grave importance. It is so important that I must insist that you activate the S-class privacy seals that you have hidden within the walls."
the Hokage reached under his desk and poured some chakra into the activation seal hidden there. He looked at Itachi with a stern expression on his face, "Very well, the seals are activated, now what is it you wish to discuss that is so important as to require privacy seals?"
The look that the Hokage was giving him would have turned a lesser man into a whimpering shell of fear, thankfully Itachi was not a lesser man so he returned the look with an impassive expression on his face. "It concerns the mangekyo sharingan," he said evenly. The new expression on the Hokage's face could only be described as a mixture of shock and fear with a pinch of awe thrown in for good measure. It would almost be humorous if the situation and subject they were discussing had been any less serious. Itachi braced himself before continuing, "I know that you have heard of it but I am certain that you know almost nothing about the ability itself. After all, it is one of my old clan's most closely guarded secrets, the very knowledge of how to obtain it could very well destroy the entire clan." Having impressed upon the Hokage just how important the need for secrecy was in this matter he pressed on with his explanation. He told the Hokage everything he and his former clan knew of the mangekyo sharingan, including: it's abilities, it's weaknesses, the consequences of its use, and last but not least the only known way of obtaining it. As Itachi spoke the Hokage's look of fear only deepened until, by the end of his explanation, it became a look of horror and absolute disgust. This of course was due to the dark nature of the power and the fact that in order to obtain the mangekyo one had to kill their best friend, something so evil that not even the most power hungry Uchiha would dare to attempt it. Itachi finished off his explanation by saying, "All of that leads me to the real reason why I have come here today...somehow I have obtained the mangekyo sharingan." the look on Sarutobi's face was almost priceless. Itachi continued, "I don't know how or why it happened but I do know when. It was while I was trying to stop my father from killing Naruto and Hinata. He tried to hit them with a grand fireball jutsu while I was fighting him. I jumped in front of it and shielded them with my chakra even though it weakened my own defense against the attack. I was blown back into a tree and knocked unconscious for several seconds, when I woke up I had the mangekyo sharingan, and the power to stop my father. But I have no idea why, what do you think happened Hokage-sama?"
Hiruzen Sarutobi, the third Hokage, known to all the world as the professor and one of the greatest ninja the world had ever seen, was nearly stumped by this seemingly simple problem given to him by a mere teenager. He was silent for a very long time, but Itachi could see his brain working, examining the situation from every angle, running through every possible scenario, and finally double checking his conclusion once he had reached it. After what seemed like an eternity to Itachi, but was in actuality about 15 minutes, Sarutobi spoke, informing Itachi of one of the most surprising explanations the old Hokage had ever heard let alone come up with himself. He began with a simple question. "Have the Uchiha ever examined the exact cause of the mutation other than the requirement of killing your best friend?"
"No, most Uchiha really don't care how the sharingan works, so they never really studied it's various forms in any great detail other than what actions are needed to obtain them." Itachi answered truthfully.
The Hokage looked thoughtful for a second before continuing on with his explanation. "That definitely sounds like a course of action worthy of the Uchiha clan, accepting the power without knowing the cause and believe it is your birthright." He said in disgust before looking Itachi straight in the eye."I believe I know the cause of your sharingan's change and why there are no recorded instances of it happening before. I'll start with the cause. I believe that the cause of the sharingan's development is strictly tied to the emotions of the user." Itachi looked surprised, the old man continued without pausing.
"Think about it Itachi, the only way for a young Uchiha to activate their sharingan in the first place is to be placed in a situation of great emotional duress, such as a life threatening situation. And now, from what you have told me, the only previously known way to activate the mangekyo form of the sharingan is to kill your best friend, an action that causes great emotional distress in the form of overwhelming grief. It seems to me that the sharingan's abilities are tied up in negative emotions, or at least they used to be. My theory is that an equally strong positive emotion experienced by the user could be enough to activate a sharingan in much the same way as those negative emotions have been proven to do. Since the strongest positive emotion is love, it would seem that you showed a love so powerful that it could override the negative aspects of the sharingan and the negative emotions that they are tied to. In fact I believe that I know the exact moment that this happened. It was once said that 'there is no greater love than to lay down one's life for one's friends', this statement seems to have proven true for you."
Itachi looked ready to object to that statement so Sarutobi clarified what he meant. "You may not actually be friends with Naruto, Hinali, and Hinata; but you felt strongly enough about them to rush to their defense when you realized that they were in danger. Once there you proceeded to fight your father, who was more powerful than you, without regard for your own life. When he tried to pull an underhanded attack on them you jumped in front of them, effectively sacrificing your life for theirs. This disregard for your own life showed a love so strong that it activated your mangekyo sharingan, which gave you a large enough boost in power that your attempt to sacrifice yourself became unsuccessful and you were able to defeat your father with your new abilities that were unlocked."
Itachi looked surprised at the relative simplicity of this explanation, it was a wonder that nobody had discovered this before! Of course the sharingan existed solely in the Uchiha clan, one of the most selfish clans in Konoha if not the entire world. Maybe it wasn't so hard to believe that this power had gone undiscovered for so long. But the Hokage wasn't done surprising him yet, his next sentences were just as shocking.
"It seems to me that the unorthodox way that you developed the mangekyo sharingan may in fact exempt you from the consequences of using it. I have surmised that the way in which all other Uchihas have obtained the mangekyo were perversions of the real way in which it was meant to be obtained, the way that you actually did. Their methods resulted in an incomplete transformation, which damaged the eyes each time they were used, which in turn resulted in blindness after continual use. If I am right, and I usually am, then you are the first sharingan user in history to obtain a complete mangekyo sharingan which may or may not result in you being able to use all of the known abilities of said dojutsu without any negative effects other than the occasional case of chakra exhaustion. Only time will tell if you can pass this purified form of the sharingan on to your children, but I suspect that you can at least in part, they will probably have to obtain the mangekyo form for themselves but I surmise that you have succeeded in purifying the sharingan completely of it's negative attributes. And to think that the elders of your clan banished you for that, I love a good case of irony."
Itachi was amazed, he hadn't expected to get the answers to nearly every single question that he had regarding his new form of dojutsu. But he had other questions as well. "Hokage-sama, about changing my name..." The Hokage held up a hand to stop him.
"That has already been taken care of, I filled out the paperwork before you arrived in anticipation of your request. But considering the information that you have revealed to me regarding your sharingan I am inclined to grant you more than just a name change. It seems that you have developed techniques unique enough that I can allow you to create your own minor ninja clan, and there's nothing that the Uchiha can do about it since they did banish and disown you. We may even go so far as to classify you as the progenitor of a new dojutsu, but that will have to wait until you have children and we see whether or not the original sharingan is changed in your descendants."
Now it was Itachi's turn to hold up his hand for silence. "Hokage-sama, I believe that I can settle at least part of that question right now." Having said that he closed his eyes and activated his sharingan. When he opened his eyes the Hokage could scarcely believe what he saw there. In Itachi's eyes was a sharingan never before seen, it was gold instead of red and had four tomoes surrounding the pupil, whereas the sharingan could only have three. Truly this was a new form of the sharingan. As far as the Hokage was concerned the Uchiha clan was full of idiots for getting rid of Itachi simply because he decided to develop a sense of morality and duty.
"Well that settles it, we don't know whether or not your sharingan has changed enough to classify it as a new dojutsu yet, but this change certainly does qualify you to start a new clan and run it as you see fit. All I need is a name and I can start the paperwork immediately, and since you already have the Hyugas as your allies I see no way that your enemies can block you from being on the council. Now, what name would you like for your new clan?"
Itachi looked the man straight in the eye and answered him without hesitation, "My new family shall be known as the Mamoru clan."
The Hokage smiled. "The Mamoru clan eh? A fitting name considering how your new clan was started. Very well, from this day forth you will be known as Itachi Mamoru, head of the Mamoru clan. It has a nice ring to it don't you think?"
Itachi smiled for the first time as he stood up to leave. "Yes Hokage-sama, I believe it does. Now if we are finished I fear that I must take my leave of you, I need to inform the Hyuga clan head of this new development so that we can prepare for the next council meeting. Thank-you and good day." Itachi bowed before shunshinning away. The Hokage sighed, why did all ninja feel the need to leave in such a fashion? He never could discover the answer to that question. Knowing the futility of even attempting to ponder that question, he instead got to work on creating Itachi's new clan. He opened his desk and withdrew the paperwork required for the starting of a new clan. As he began to fill it out his mind began to wander, his hands writing of their own accord, he had held this job so long that he didn't even need to see the paper to know what he was writing. 'Itachi Mamoru, he mused, perhaps you would be a good successor for me. Nobody else has proven worthy, and any who comes even remotely close will not protect Naruto as he needs them to. But you have already proven more than capable for that task. Perhaps I can retire sooner than expected'. By the time he had finished the last form the old worn out Hokage had made his decision. Itachi Mamoru would soon be the Godaime Hokage, and Naruto's newest protector on the council.
Side Note: fugaku hasn't woken up from his coma yet, he keeps reliving the genjutsu over and over again in his mind because of how powerful it was. How's that for bad luck? Something like that could ruin your whole day. If he ever does wake up i doubt he'll be very happy with how things have changed.
A/N: how's that for consequences eh? the uchiha have succeeded in getting rid of one of their greatest ninja who has just succeeded in raising his sharingan to a level never before thought possible. and in doing that they have unintentionally just created a rival clan of sharingan users as well! In less than a week the uchiha have lost their clan head, their greatest ninja, much of their respect within the village, and their position of power on the council (who besides danzo would support them after what fugaku just did?). And now they have lost the only thing that they can't get back, their position and notoriety as the only clan of sharingan users, do you think that the civilians will tolerate the uchiha superiority complex when there is now a clan with the sharingan that doesn't think that they are superior to everyone on earth? I seriously doubt it. Of course true to form the Uchiha won't see this as their fault, even though they directly caused all of it, no they'll find somebody to blame. Who do you think it'll be? Naruto of course, and by extension the Hyuga clan and Itachi too.