Itachi is the crippled one (because he spent months lying down in a coma and no one bothered to move him around so his tendons and muscles wouldn't atrophy) and the blind one (because his eyes are in Sasuke's head), so Itachi is the one who sits all graceful and too-thin and plays the koto, plucking string after string in heart-rending melodies (because even if he can't see he can still remember seeing that courtesan playing, years and years ago, and the Sharingan bloodline is more than just vision.)
Sasuke is the one who pretends to be his bodyguard, because he's the able-bodied of the two, and because they've got to make virtues out of their necessities and Sasuke's biggest necessity is to kill anyone who even looks at Itachi wrong.
Itachi is the blind one, and the crippled one, and the less scary one (he could kill them all if necessary, Sasuke believes that, because his big brother is the most powerful ninja he's ever met, but he also believes that he will die before making it so Itachi has to.) He's also much better at genjutsu and other, deeper transformations.
So when they go incognito Itachi is the one who changes the most, makes himself a child, makes himself an old man.
Makes himself a woman.
He looks like their mother must have at twenty, if their mother's skin had gone translucent from poor health and months buried alive in a cave, if her hair had grown uncut to her waist, if a black blindfold over her eyes made it so there was nowhere to look at but her pale, parted lips.
It's like all the dead women of their family come to half-life in one, ghosts at the edge of dawn.
It twists in his guts, it burns, he hates it. He hates himself.
'Next village we'll say that you're my wife,' he says one day, brusque and guilty, angry. 'I'm tired of having to beat up all those idiots.' Those who want to abuse a defenseless woman, those who she fascinates with her otherworldliness, those who want to protect her.
Especially those who want to protect her. Him. Itachi is his brother, and he will never go off and 'have a good life' with some simple, brave, noble-minded farmer. It's not even that they're so ridiculously wrong about what they believe would be a "good life" for Itachi.
Itachi will never go off because Sasuke will never let him. He is not losing his brother a third time.
(He is not losing his motherfamilycousinwife again.)
The night he snaps he could blame it all on the alcohol. He could lie that the servants finding the sheets clean would find their cover story strange. He could say the truth, say that either he does this or he kills that laughing man who dared to come up to his brother and lift long black hair to his lips, as if because he is daimyo and it would spark a war this means no one can say a thing.
He could say the deeper truth, that he's wanted to do this ever since he found Itachi's unconscious almost-corpse deep in Madara's lair, to crawl into his skin and stay.
He doesn't say a thing. He makes sure he can't, mouth busy. He kisses his brother quiet, mouths his neck, those breasts he shouldn't have, those too-thin arms, each and every rib he can feel through his skin. The cradle of wide hips, like their mother's, he imagines. Lower.
There's no struggle. He keeps a hand on Itachi's mouth to keep his words inside anyway. He doesn't want to hear a no.
They never talk about it again. Not even the next night, when Sasuke lift the hair off his brother-wife's nape and kisses it and pushes himself inside his brother again. Or the one after that.
At the end of the second month, end of winter, they leave the daimyo's court, and a courtesan congratulates them on their child-to-be. Itachi doesn't say anything, though Sasuke knows he cannot have failed to hear.
His guilt would consume everything, but the sick satisfaction refuses to stop burning. He can't bring himself to touch Itachi again, or to stare too long as his rounding belly. Itachi might be blind but somehow he always knows.
The child is born, a boy. They have no name for him. Haven't discussed it. Haven't discussed anything. They're by the ocean, so the midwife suggests Kaiki.
Sasuke knows she means "sea breeze", but writes it as "death anniversary."
When the midwife has gone, Itachi's fingers read the lines left in the paper, and he sighs and feels for Sasuke's forehead and flicks it.
"Revival" it is.
Sasuke crawls into his brother's arms and for the first time in years he cries.
They make plans to settle elsewhere, for good, forever. When they leave that village on the edge of the ocean, Itachi is a man again. Sasuke is not. It's his turn now. His penance. His redemption.
Kaiki roots against dry breasts and doesn't seem to know the difference.