Familiarity
Kira knew everything about his captain.
He's been taught how to move, how to submit, how to enjoy the pain his captain inflicts because there's nothing else he can expect from Gin but pain mixed in everything.
Their sex is like that, the indescribable fusion of pain and pleasure that leaves Kira gasping/moaning, bleeding/whole and sated/unsatisfied all at once.
Gin's weird like that. So is Kira, since he can't get enough of it and still thinks on the edge of his thoughts every night, no more.
Sometimes Kira thinks Ichimaru-taichou can read his mind, because whenever the thought shows up in his mind (before the pleasure explodes and when the pain peaks, with his captain entering him from behind and licking up Kira's blood from an angry bite mark on his shoulder) Gin purrs his name, soft/commanding, kind/malicious and arousing/terrifying all at once, bringing Kira's mind off his morals and back onto the fact that he's on his hands and knees in Gin's room bleeding and leaking all over the floor.
Right after that he's lost, the pain blurring into pleasure and sharpening back again.
Gin's quiet when he comes, just a sigh of pleasure in Kira's ear, but the locking of his limbs makes Kira think that his captain takes just as much enjoyment in this as he does.
Kira likes to think this.
After they're done Gin carries Kira back to his room, making him feel coddled/condescended (Ichimaru-taichou is so strong) and ashamed/thankful (is Ichimaru-taichou carrying him back for his own reputation or Kira's or just because he doesn't want to see Kira's face?) and weird because in the first place he's just been fucked so hard he can't walk, and it really is always a good fuck, and in the second place because he's just been fucked so hard he can't walk, what kind of slut is he?
When Ichimaru-taichou brings him back he tucks Kira in completely naked, with patronizing pats on the head and one last wet, open-mouthed kiss goodnight kiss that ensures Kira doesn't sleep for at least half-an-hour after that. Ichimaru-taichou's hand lingers in Kira's hair after one last "sweet dreams, Kira-kuun" and Kira feels safe even though he's bleeding on the sheets, because Gin is the captain he trusts with his life.
Gin is the man who screws with Kira's mind and body and makes him utterly dependant. Gin is traitor, Gin is not the captain who keeps his men alive, Gin is playing executioner to a man who makes Gin's own tendencies look like the wet dreams of a rabbit on Ritalin.
Kira Izuru knows his captain very well, and not at all.
-end-