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Niji was pretty sure he had never wanted to put his cock in anyone's ass as much as he wanted to put it in his long-lost brother Sanji's. Ever since that disaster of a wedding, he couldn't stop thinking about him. The only reason he had stopped waking up hard with Sanji on his mind was because he had started making sure to jack off about it before bed every night.
As he stroked his cock, Niji imagined his brother whimpering as he entered him. He imagined every desperate 'no' turning into 'yes', until Sanji was begging him to fuck him harder, desperate to come on his cock.
Sanji struggled in his brother's grip, but he wasn't strong enough to throw him off. He wasn't strong enough to keep Niji from ripping off his clothes. Though he was far stronger than he had been when they were children, he was still helpless to stop whatever his brother wanted to do to him. And it was all too clear what his brother wanted now.
The thought was nauseating— as compelling as it was terrifying. Sanji's stomach twisted, but that didn't stop the pulse of arousal between his thighs when his pants came off, and Nji's hand explored his cock and balls. Not just another man's hand, his brother's hand.
"Stop! What the hell do you think you're doing? This is sick!" Sanji's mouth felt dry as he protested, grinding involuntarily against Niji's hand even as he did.
"Relax, little brother. The rest us have been doing this together for ages. You've been missing out."
Two lubed fingers suddenly pressed into Sanji's asshole, and he couldn't make any reply but a shuddering moan as his brother stretched him open.
"See?" Niji leered, "Your body knows what it wants. We're flesh and blood, Sanji. Nobody will satisfy you like one of us will."
Sanji's head spun, dizzy with a sick mixture of lust and humiliation as his brother worked his fingers in his ass, pressing against the sensitive spot inside him again and again, and making the tip of his cock ooze with pre-cum.
"Stop, Niji," Sanji whimpered, but his brother was right, he did want this. How much had he been missing out on all those years he was gone? How lucky would he have been to stay and get used and passed around as his brothers and sister's fuck toy?
Niji felt his brother surrender to the pleasure that he gave him, and it sent a lewd shudder through his body. As he pulled his fingers out of him, watching the way Sanji's asshole pulsed with need as he did, his gaze swept over his limp, submissive body. It was so much like his own, but smaller, softer in places, his pale hair and little goatee begging to be tugged.
Niji slapped his ass hard enough to leave a mark, and Sanji gave a strangled gasp. Niji grinned and grabbed his brother's hair at the nape of his neck, arranging him properly on his belly and knees below him. He gave himself another moment to savor the sight, then he took what he came for.
Niji pressed his cock slowly into his brother's greedy asshole, taking it slow just to watch Sanji's reactions. He watched all the muscles in his back and shoulders tense, and licked his lips as Sanji let out a whine.
"Niji, you can't do this, we're brothers…" Sanji protested lamely as Niji filled him.
His fingers tight against Sanji's scalp, Niji leaned in and rasped in his ear. "We're brothers. That's why I know just how to fuck you the best."
Niji jerked Sanji back by his hair, forcing his cock the rest of the way inside him, balls deep. He felt Sanji's hole pulsing and twitching around him, and his own cock throbbed with desire, finally sheathed exactly where it wanted to be.
Sanji whined again, and Niji decided he loved the sound, loved the way his brother writhed underneath him like he couldn't decide if he wanted to escape, or try to take Niji deeper. He started to fuck him, slamming his cock deep every time, starting with long, slow thrusts.
Sanji panted and whined again. Niji could see his fingers clawing the gorund, tense and desperate.
"Stop, Niji. Please… Oh fuck."
But Niji didn't stop. He rode his brother's ass like a toy he didn't mind breaking, faster and harder once he hit his stride, rocking his hips down with every motion, pulling out a few blond hairs in the tight grip at the nape of his neck.
It felt so good to take him like this, to use him. This was what his weak little brother was made for: a whining, whimpering sheath for his cock. A beautiful, soft hole for his cum.
Eventually Sanji stopped saying "stop", but he never stopped saying "please". By the end of it, Sanji was begging over and over again, breathless, demanding to be fucked, whimpering for his brother to please come inside of him, to please make him come.
Niji let go of his brother's hair and wrapped one hand around his throat instead, jamming the fingers of the other into Sanji's mouth. Sanji's whimpers were smothered at once, replaced by gulping and gasping, and Niji's balls throbbed at the sound; at the feeling of Sanji's throat under his fingers.
He rode him down into the floor, squirting thick jets of cum deep in his brother's asshole as he gasped and choked. Niji felt him come under him, his hips bucking weakly against his assault.
Niji held him tight, holding his cum inside him, holding his throat until he was on the verge of passing out, before he finally released him. As Sanji moaned and shuddered, Niji slid his cock out of his ass, and watched it twitching, a dribble of cum rolling down the cheek.
Niji made a thick noise at the back of his throat, the image of his cum drooling out of Sanji's ass sending him over the edge. As he gasped and squirted over his own stomach, he became aware of Ichiji standing over him with a smirk.
"Thinking of our missing brother again?" Ichiji drawled. He swam in Niji's vision. "I heard you say his name."
Without shame, Niji grinned up at him. "Yeah."
"Then you'll be pleased I have a plan to bring him back to us. Now spread your legs, I haven't gotten off yet tonight."
Obediently, Niji arranged himself for his older brother's cock. Even though he'd just come, he was already getting hard again at the thought that soon they'd have their missing brother back where he belonged.