"I entrust my left eye to you, Itachi,"

If Shisui is a river, Itachi is a tadpole swimming around inside it against the pull of the current, just trying to survive. That is how he feels when people compare the two up-and-coming Uchiha geniuses. It's like trying to put a name to a feeling that no one has experienced before, and Itachi wants to explain that to them. He wants to shake them until it sinks in and then throttle them for suggesting Shisui is anything less than he is. He is so much more than Itachi, and he wants to make sure everyone understands.

He doesn't, of course, because he is a reserved young man with a good conscience and a better perception of the world than his clanmates give him credit for. Telling his cousins and aunts and uncles that they're wrong, that Shisui is a shinobi cut from a different stone, a higher calibre of rarity, they wouldn't understand. He knows that. That's why he nods and shrugs and keeps his mouth shut because he doesn't want to cause a stir, not with all that's already going on.

Itachi swallows the apprehension in his throat. It's useless to feel nervous, what's going to happen is going to happen and it's all going to be inevitable. He can't stop it anymore than he can resist its pull, like the tug and sway of the Naka river or maybe like Shisui's warm hands when they lead him into the sunlight. He thinks their fate is something that's been written in stone, carved into their destiny like a kunai through the bark of a cherry tree, since the day they were born.

"You're a part of me, Itachi."

"And you me, Shisui."

Sometimes, Itachi feels like they're the same person split down the center and housed in two separate bodies. Shisui is his everything. The air he breathes, the water he drinks, the food he eats, the days he lives; Itachi shares them all with Shisui. He shares the nights especially, like when he finds himself at Shisui's window in the bleak blackness and drags him out into the moonlight. They watch the stars and the moon for hours as it crosses over them, and they see shooting stars sometimes.

"I wish it didn't hurt." Itachi says, and Shisui turns to him with crumpled eyes and a tense jaw.

"I know, Itachi." And when arms are settled around him, pulling him closer into the warmth, he leans closer. His lips press hotly to Shisui's collarbone and he feels a warm mouth descend upon his brow. It's like being in a sanctuary without having left anyone behind, and he knows that Shisui is the only one who can do this for him. He relishes in it while he can.

"I know." Shisui repeats, his warm breath fanning out over Itachi's forehead. The night grows cold but Shisui remains a furnace, and Itachi can't help but wonder how he can thaw the ice off of Itachi's skin like it's not even there.

"Take it while I still have the option to give it to you."

Itachi wants him so much sometimes he physically hurts.

He wants arms around his waist, spidery fingers in his hair, lips pressing to his forehead, and most of all he wants to feel his heart beat in tandem with Shisui's. He wants it so much he thinks he could just about die. When Shisui comes back from an extended mission, three weeks without sign or notice of his being alive, Itachi really almost does.

The moment they are alone he wraps his arms around Shisui's waist and squeezes so tight his muscles start to tremble. He bites into his lip so hard that blood wells up from inside, rolling onto his lips and turning them the colour of his mother's darkest lipstick. He might have felt embarrassed but Shisui is massaging the back of his neck and running his fingers through Itachi's hair, so Itachi just lets it all go.

Only Shisui has ever gotten this out of him. Only Shisui.

Only Shisui.

They've been on a number of missions together, but Itachi remembers one of their last the best. They both had a significant near-death experience that drove them even closer together, if that could've been at all possible.

Itachi remembers flashes, snippets of a fight with a rogue ninja; a deserter; a missing-nin. It's branded across his forehead in the form of his headband, slashed through the center with a deliberately cut line. He's a defector from Kusagakure and he's not quite as fast as Shisui, but Itachi will be damned if he's seen anyone make it quite so close. He speeds around them, around Itachi in circles and around Shisui in half circles that he tries to complete but never actually manages.

It's all going well because they've got a strategy for lightning fast opponents like this one.

And then Shisui hesitates, Itachi can't figure out why, but he's faltered where he can't falter and suddenly there's a kunai moving almost faster than his eye can follow, and it's heading straight for Shisui's exposed throat.

He moves faster in that instant than he has ever moved before, and probably ever will again.

He dives between the two of them, acting as a human shield. He lost his concentration, lost control of his jutsu, lost everything, just to get between them. He's got a kunai up to defend himself but in terms of speed there's no contest and the missing-nin's knife ends up stuck straight through his throat. It's in one side and out the other, in the most horrifyingly literal sense.

When Shisui turns around his face goes from a pale shade of horrified to a crimson shade of furious.

He's never seen Shisui move that fast before, and probably never will again.

There's half a second of silence and then a loud crack, one that sounds like bones slipping free from bones and Itachi already knows Shisui just broke the man's legs. He can't be sure because he can't see, he's presently lying sideways on the ground breathing with the untimely elegance of a fish out of water, but he knows enough about Shisui to know that when he gets angry, he doesn't go for the kill. He maims and seriously injures, but if you personally infuriate him then he goes for lengthy bodily harm rather than a swift execution.

Most Uchihas are like that, actually.

The thought is amusing until he passes out due to blood loss and has feverish dreams of a river, an eyeball rolling in his hand that definitely isn't his, and Shisui limping away from him with the stern, rigid back of a man who faced down his fears and has turned them into strength. He's vaguely aware in all of these dreams, slightly varied in detail each time, that he's crying great big tears of remorse and helplessness. He's cracked and vulnerable and Shisui doesn't look back, not even once.

That dream hurts more than the semi-healed hole through his throat when Itachi wakes up, gasping for Shisui, Shisui, Shisui please.

He's there, though, to quell Itachi's slowly mounting hysteria. He breathes warmly over his brow, kisses each eyelid, strokes the sides of his face and traces his jawline into his hair, and presses so close that for a while Itachi isn't sure where he ends and Shisui begins. He's so tired, so wiped clean of chakra or energy or the motivation to do anything but laze in Shisui's warm arms, that when the nurse comes to bring him his food Itachi refuses to eat or part with Shisui.

He threatens to run if she makes Shisui leave his side.

The nurse hastily explains the situation to the head nurse and the head nurse just clucks and shakes her head, saying 'if he wants the boy to stay so damned much then let it be, Shizuka, let it be.' Itachi thanks the universe for decent people with decent heads on their shoulders.

Shisui, meanwhile, is cackling like a madman at Itachi and the nurses and nuzzling into the crook of his neck like a great big cat. He even starts to purr a little when Itachi slides his finger through his hair, and it's the warm humming noise that means Shisui's already so settled Itachi probably didn't have to fight the nurses for him to stay. He wouldn't have allowed himself to be moved anyway.

"You're my best friend and the only one I can count on..."

In Shisui, Itachi sees so much of himself that sometimes it's a little unsettling.

He sees his immense sadness and understanding mirrored in those dark eyes. He sees reproach at the Uchiha's wrath buried there, and disappointment in the method Konoha is using to deal with them. When Shisui picks Sasuke up and throws him over his shoulder, he sees affection. Infinite warmth that could engulf a small planet. When he looks out over the river with those distant eyes, gazing steadily into the horizon, Itachi sees a vast empathy that turns weary the longer he looks.

They are geniuses and they speak a different language. It consists of shared glances, whispered words, gentle emotion, and a woefully precise understanding of the world and where it's going to end up if they don't do something about it.

Sometimes people mistake Itachi for an emotionally numb automaton, rather than a human being. He can't blame them for it, it's not like he's done anything to help his case. He feels a lot; immense waves of feeling that crash over him in the middle of the night, belated reactions to lost comrades and the future fight, they all make sure he realizes that for himself. So he plasters on a mask of indifference and stony apathy during the day and opens up for very few. Sasuke sees him sometimes, and he wants his little brother to see him smiling, because he doesn't want his baby brother to remember him as an unfeeling machine. Everyone else can do that, but not Sasuke.

Please not Sasuke.

Shisui sees him too, although not for the same reasons Sasuke does. Itachi didn't let him in, no, Shisui knocked politely once and then kicked the whole door down. He slammed the brakes on Itachi's desperate speed and slowed him down, made him collect himself and change his pace so that he could live and not run headlong into his death. Every time Itachi feels a defence going up, Shisui brings it back down with a blinding smile, or a playful wink, or a lilting laugh that has Itachi's heart pressing painfully against his ribs.

But Shisui wears a mask too, and Itachi has to fight the feeling of comfortable stillness to reach up and take it off.

Itachi has never seen Shisui cry. The closest he came to seeing tears was when Shisui received a message that informed him both of his parents had died fighting in the war. They had been young, so fragile and malleable at that age, and yet Shisui hadn't shown a single crack in his defences. He nodded and walked away with a stiff upper lip like the bravest shinobi Itachi had ever known. There was no one he wanted to be like more than Uchiha Shisui in that moment, and no one he wanted to comfort more.

Itachi found him crouched on his parents bed with shaking hands and a newly awakened level of sharingan. All he could do was stand awkwardly in the doorway until Shisui told him to close his eyes. When he did, Shisui plastered himself to Itachi, clung like a kitten to its mother, and refused to move. After a while Itachi slid down the wall with Shisui in his arms and they remained there for the night, stock still against the stagnant air in the Uchiha compound that night.

When the sun rose blood red the next day and Shisui finally pulled away, out of the vice grip Itachi had around his shoulders, carmine stains tracked down his face like phantom tears masquerading as scars of war.

"I love you, Shisui. I love you. I love you. I love-"

They are twelve when they kiss for the first time. It's just a chaste little peck that Itachi presses to the corner of Shisui's mouth, 'a good luck charm,' Itachi says, even though he doesn't believe in luck and he knows Shisui doesn't need it. He does it anyway because it feels right, and because Shisui's eyes light up in a way he's never seen before.

Itachi never thinks of what they have as a relationship or a friendship because it's an amalgamation of the two of them. They simply exist together; the simply are. They are Shisui and Itachi, Itachi and Shisui, and they have been best friends and geniuses and speaking a different language together since the day they met as toddlers.

There is no one Itachi trusts more than Shisui, and there is no one Shisui has more faith in than Itachi. When they breathe the same air, as close as two people can be, they share these facts with each other without speaking a word.

"I know, Itachi,"

Sometimes when Itachi wordlessly informs Shisui that he loves him, he doesn't think Shisui gets it. If Shisui were to die or disappear or leave the village, abandon Itachi and move on, Itachi's life would be over. He wouldn't die or kill himself or anything so futile, his village still needs him after all, but his life would be over. That would be the end of Uchiha Itachi, the village's second Uchiha prodigy, a boy who would willingly lay his life down for but three things, and it would be a very quiet, subtle ending. No one would notice until the very last moment, the very last second the light slipped away from his eyes, and only one person would be around to see it.

Sometimes Itachi thinks Shisui doesn't understand.

"I know."