"Don't fuck him again," Sasuke is begging in those tiny gasps, the kitty 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's turned into, breaking into. It will be Itachi's cage bird, staying up waiting as long as needed, till Itachi comes home from wherever he's been.
That's 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. 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 kitty 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, moans and gasps. 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, deep enough to never really heal away. Afterwards Itachi had fed Sasuke his own blood off of his fingers. "It's my blood as much as yours, don't you agree?" had been the message, "It's you, but 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 posses, and as such, 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 was high on Sasuke's unnatural love, and how it surged through his little body with such shuddering pain. 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.
Sasuke's pale skin looked good when stained by bruises. Itachi's favorite ones were bite marks and hickies. 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 sound of their slapping skin and the kitty mewls, the boy's thin arms holding on to his violently rocking body by his neck, all this made Itachi promise to himself, wholeheartedly, to not go and see Kisame again. He promises with a rare kiss.
With the morning always came change of heart, however, and Itachi wasn't one to stick to promises he had never even pronounced.
Sasuke was.