Itachi hadn't come back right.
He stares at nothing. Sometimes he looks at Sasuke, who likes to imagine that Itachi can see him, even though he knows better.
Itachi never speaks. The only sounds Sasuke can coax out of him are gasps and soft moans. Sasuke talks to fill the silence. He doesn't know if Itachi listens, but he likes to think that he does. He hopes that he does. Sasuke, who had never been fond of words, speaks enough for them both.
It is just the two of them, living quietly in a small house at the edge of a forest, far from Konohagakure, far from any ninja village. They've earned this, Sasuke thinks, and says so to Itachi. They've paid for this with blood and tears and suffering and death.
Sasuke's team has long since dissolved. Only Karin stayed long enough to witness the full extent of Sasuke's obsession. In the end, when Sasuke was beyond reason, she left him standing in the remains of one of Orochimaru's hideouts, searching through crumbling scrolls with bloody hands.
The knowledge he'd scavenged hadn't been enough on its own. He'd had to find Kabuto, half-mad and twisted into something no longer human, to complete the jutsu. The results hadn't been perfect. Sasuke wonders if Itachi would have turned out better if he'd used a different sacrifice. Too late to think of that now.
Sometimes, when the moon is full, Sasuke finds Itachi standing outside with his face to the sky. He sways gently, as the branches do, and Sasuke has to lead him inside. Sasuke can not bear to see moonlight on his brother's skin.
He draws the curtains closed and pulls Itachi into bed. His kisses are met with no resistance. He mutters bittersweet nothings into Itachi's bare skin and sleeps as peacefully as he his able, wrapped in darkness and Itachi's arms.
His dreams are full of people he once knew, but their faces are starting to blur and they are fading away like memories of a past life. He doesn't think about his old village anymore. He doesn't think of the people he once called teammates. All that matters is the world he has created for himself and Itachi, which consists of only them, hidden safely among the trees of a distant land. Even if Itachi isn't quite right – and Sasuke has enough sanity left to know that he isn't – this exile is the closest thing to happy ending he will ever know.
And that's good enough for him.