Note: This is something I came up with a little while ago. It will take the form of several mostly chronological vignettes from various characters' points of view. I post on AO3 first under the name Hei.
Summary: Shisui watches as his clan and the village fall ever closer toward open violence and realizes, he has the power to take control.
Shisui isn't sure how he feels when he finally manages to corner Itachi and forces him to talk. He's not really surprised to find out they're actually going to attempt the coup. Fugaku is a belligerent fool who has never been able to forgive or forget, and he listens too closely to the angry mutterings of elders far too interested with personal power and glory. Shisui can't summon the stark dread Itachi radiates either. Even as he sits next to Itachi and hears the fear lacing his voice, Shisui can only see the innumerable possibilities a coup represents.
It's times like these that Shisui wonders if he is evil. His mind is too quick to spin through different eventualities, analyzing each potential outcome. Even while he sits and offers empty assurances for the future, his mind sees ways to bring about the end in a wash of flame. It is times like these where Shisui scares himself.
If he were Hatake, he would probably have taken Itachi with him and immediately reported the coup to the Hokage. But he's not. He is broken in more dangerous and less predictable ways. A small voice that sounds disturbingly like Itachi's own begs him to do his duty, even if he waits until after Itachi himself has fallen asleep. The Hokage must be told. But he can't bring himself listen to it, not now. His mind is buried in consequences and probabilities.
As the moon begins to set, Itachi's breathing evens out, and he relaxes against Shisui's arm. His warm weight anchors Shisui and serves as a constant reminder of who will pay most dearly should Shisui act rashly. And, for all that Shisui knows Itachi is too idealistic and trusting, he cannot bring himself to take advantage of that fact. Itachi is his only real friend and his conscience. He would do much to protect him.
Life goes on, and Fugaku and the Hokage spend increasing amounts of time together. It's funny how well threats of violence facilitate negotiations. Shisui is unsurprised to note an increased ANBU presence watching the district, and though he is never assigned that particular duty, he knows Itachi is. But even while his companions burn under the indignity of the village's watch, Shisui is too busy weighing his options to pay them mind.
Itachi does not handle the stress nearly so gracefully as Shisui. As tensions mount, he retreats inward until some days he doesn't respond to even Shisui's prompting. He doesn't eat unless pressed and spends most nights on the rooftops, crying silently from the weight of expectations. Some nights Shisui comforts him, but too many he finds himself pushed away.
While always skinny, Itachi becomes gaunt. He is killing himself and no one says a thing. Shisui offers what support he can, but even he is not enough anymore.
Itachi's thirteenth birthday draws near, and Shisui is ordered to spy on him. Not that Shisui wasn't already following Itachi, constantly reminding him to eat and periodically forcing him to sleep. Despite it all, Itachi still goes on assignments, still interacts with his family and manages to fool almost everyone into believing he is coping well, that he is just tired from endless missions and reports. How they ignore the lost weight and haggard despair, Shisui doesn't know. Even with Shisui's intervention, Itachi isn't eating more than one meal out of every three and he's sleeping even less.
It isn't until Hatake Kakashi asks to talk to him alone, that Shisui realizes that someone else cares. Hatake casually remarks on Itachi's recent promotion to captain, nominated by Danzo himself. While Shisui had heard about the captaincy, he hadn't known the details. Even in ANBU there are secrets. Hatake also mentions that Danzo has taken particular interest in Itachi, that there are rumors Danzo is working with Itachi on a failsafe, should tensions with the Uchiha increase. Shisui is both thankful for the information and stunned. How had things escalated so far? Hatake is gone before Shisui can begin formulate a response.
After that everything begins to fall apart, crumbling like a castle of sand. Shisui sits on the rooftops at night, listening to Itachi's ragged breathing and thinking about the future. Mostly they sit in silence, though sometimes Itachi will speak. One night, he looks over at Shisui and asks what it means to be good, if he believes it is possible to do evil in the name of good and still be good. Shisui has no answer.
Shisui knows without asking what Danzo's plan is. For no matter what else they might be, the hidden villages are military establishments. That Danzo would be so cruel as to order Itachi to wield the blade is also no surprise. Shisui only escaped his grasp through careful avoidance of politics and acts of borderline insubordination. If he had been clan heir, not even those would have kept him safe. He also knows that his eyes have the power to stop the coup, nonviolently, before it can happen. He has known he could since Itachi first told him what Fugaku was planning, and he has kept silent as his best friend began to shatter.
Shisui knows he is not a good person. His success as a ninja is proof enough of that. He is a selfish but pragmatic person. And he knows he must act before Danzo. With Kotoamatsukami, it would be easy to force Fugaku and the rest of the clan to abandon their plans for a coup. Not even the sharingan can combat his genjutsu. The problem is, of course, that that would only treat a symptom. Many of the clan's complaints have merit. Change needs to happen on both sides, and Shisui knows people well enough to recognize that once the Uchiha are no longer a threat, the village will stop negotiating. That's why this is not his first plan. This is not the one he thinks will work. This is, however, the more honest plan.
Shisui's first plan was to use his genjutsu on the Hokage and council. If he were to become Hokage, it would not be difficult to soothe the Uchiha and the village. He knows what needs to be done, and he knows how to do it. He isn't sure though, if he should. Of all the people Shisui knows, he is probably one of the worst candidates for Hokage. He is too selfish, he enjoys power and manipulation too much. He is not a good person. If Itachi were older the decision would be simple. Shisui knows he can trust Itachi with his and the villages wellbeing. He knows that Itachi would eagerly suffer a fate worse than death to protect his village. But Itachi, even if he is an ANBU captain, is still a child and still too young. So Shisui remains indecisive and hesitant to act. If he takes the hat this way, he will have betrayed his village and his clan, but if he does not, he risks a civil war.
As he prepares for a mission, a routine assassination, Shisui thinks on Itachi's question from so many nights before. Is it possible to do evil in the name of good and still be good? He didn't have an answer for Itachi then and he doesn't have one now. But, he supposes, it doesn't really matter, because no matter how many good or evil deeds he does, Shisui knows he has never been truly good. And as he thinks on that fact, he realizes his mind has already been made up. He has known for months what he is going to do.
It is almost too late when Shisui decides to act. He finds Itachi by his locker in the ANBU headquarters, already in uniform, staring despondently at his blade. "Do you trust me?" He asks Itachi, his voice calm, betraying no inkling of his tension. He does not need Itachi for this, in fact it would be kinder to leave Itachi out, but Shisui wants someone to support him, someone to know the truth. Itachi nods once without looking up from the sword. "Would you follow me without question?" Itachi nods again, only now turning to look at Shisui's face. His eyes stare into Shisui's lifelessly, and Shisui wishes he had acted sooner. Faking a grin, Shisui nods, "Good, then I have a plan to peacefully put an end to this coup business once and for all."
Itachi stares at him, hope flickering dimly in his eyes. For the first time in months, there is something approaching life in him. As curious as he is, he is true to his word and asks no questions, merely following Shisui a step behind as they make their way to the Hokage tower. Shisui wants to tell Itachi the plan, but fears he will lose his nerve if he stops. Instead, he tells Itachi to trust him and instructs him to act as a bodyguard. He tells him that if all goes to plan, no one will die. He does not say that he is dragging Itachi into another coup. One that utilizes stealth, betrayal and surgical precision instead of armies and force. He rather doubts Itachi would approve.
They scale the tower and use ANBU codes to easily clear security check points. With Itachi behind him, he is beyond reproach, none dare question what brings them to the tower with such urgency. They barge into the Hokage's office and Shisui wants to smile. The council is already present, and while Danzo isn't here, he is not typically involved in the selection of the next Hokage.
There is movement behind them as the Hokage Guard step forward. Not even Itachi's presence is enough to calm them. Acting as the bodyguard he was ordered to be, Itachi shifts into a more aggressive stance. Itachi really is, Shisui notes, very good at following orders. When all of them turn their focus to Itachi, he knows he has won. He can feel the tendrils of control latching onto their minds. The genjutsu is most vulnerable when it is first cast, but once it has merged, it is very difficult to dislodge. Shisui has not had many chances to use his mangekyou, but he wields it with intuitive mastery, planting memories of meetings that never took place and suggestions of ideas that were never had. Shisui can feel Itachi stiffen as he recognizes the technique, but he trusts Shisui enough to remain silent.
Shisui suddenly drops to one knee and Itachi follows. "Hokage-sama," he says, head bowed, "you wished to see me?" The Hokage blinks and looks first at his advisors, then at Shisui. Already his guards have melted back into the shadows, having forgotten why they ever left.
"Shisui-kun," he smiles kindly and if Shisui were a better person, he might have felt more guilt than relief for what he has done. "How would you like to become Hokage?" The Third continues, not pausing for an answer, "I've been getting tired since before Minato-kun took over and recently thought about stepping down again. After talking things over with my advisors, we think you would make an excellent candidate. And now, with tensions between your family and the village how they are, I thought it might make a nice gesture of goodwill to pass along the hat. I'll still be around to offer advice, but you'll be the one running the village. Besides Kakashi-kun, you're probably the most qualified ninja we have, and with your youth, I think you'll do an excellent job reinvigorating the village."
Shisui bows his head low enough to obscure his face. It worked. It actually worked. Keeping his tone as emotionless as he can, he replies, "I would be honored."
The Hokage grins and says he will take care of notifying the proper people. The appointment won't take effect until next month, but until then, Sarutobi-san wants him in the office every day, learning everything he can teach.