"Don't fuck him again," Sasuke is begging with those tiny gasps and kitten mewls. "Please, please don't fuck him again." Itachi cums so hard to that sound, the sound of Sasuke's desperation, his broken heart. His fifteen year old heart, locked away like the fluttering little cage bird it has turned into, broken into. It is Itachi's cage bird, staying up late, waiting for as long as it takes until Itachi comes home from wherever he has been.
That is why Itachi lets Kisame keep biting down over his neck and shoulders, why he lets him grab his hips, week after week, and reduce him to less than Itachi could really bear to be, if it wasn't for the greater cause. And if it wasn't for that Kisame was damn good at what he did.
Itachi comes home with shark bites lining his neck, smelling of alcohol and more than merely friendly company, to hear Sasuke's kitten mewls. "I'm all yours, I'm yours, yours, yours. Have me, please, have me always. Don't fuck him again, I can be your everything, please just don't fuck him again." That's what they really say, his whimpers. Sasuke never screams, he pleads in whispers. A tiny lick under Itachi's chin.
Itachi just rips him in two.
Itachi could make Sasuke do anything for him. He had him cut in Itachi's name into his inner thigh to prove it to him once, deep enough to never really heal away. Afterwards Itachi fed Sasuke his own blood off of his fingers. "It's my blood as much as yours. You're just a small piece of me."
Sasuke can be as faithful as he pleases, but no one can ask of their big brother to be faithful back, to demand they limit themselves to incest as their only release.
Sasuke wouldn't be selfish.
Itachi wasn't one to love, he was one to possess, and he wouldn't let his puppet tear a single thread without proper punishment. Sasuke loved and endured the punishments with a passion. He knew he deserved them. And he loved the attention.
Itachi got high on Sasuke's unnatural love, and how it surged through his little body with such shuddering pain. It was a cleansing pain he caused, it cleansed them both, wiped everything else away. Then he woke up, every other morning with several of Sasuke's pulled out hairs tangled between his fingers, with his little brother's blood dried on his lips, and the boy's cum in his long hair. A line of distaste would appear by his mouth before he got out of bed to wash Sasuke off of himself.
Sasuke's pale skin was so easily stained and marred. Itachi favored bite marks and bruises, lovingly crafted and left to fade. Sasuke loved them too; he loved the attention.
Itachi saw himself in Sasuke. They smelled the same, their hands were the same, their hair was the same raven. He saw potential in the boy, and pride rippled through him at times. He was his own flesh and blood, and sometimes the silent pleads, the little kitten mewls heard over the sound of their slapping skin, the boy's thin arms holding on to him for dear life by his neck, it made Itachi promise to himself, wholeheartedly, to not go and see Kisame again. He promises with a rare kiss.
But with the morning light always came change of heart, and the line of disgust would reappear by his mouth. Itachi wasn't one to stick to promises he had never even pronounced.