In a poly Akatsuki scenario, Souma encourages his seniors to do anything they want to him as an extension of his duty to serve his lords.
Keito and Kuro both take time to warm up to this oddly kinky dynamic, they both see Souma as someone innocent and worthy of protection, but Souma literally gets off on them getting off. No matter what they do to him, he loves it, like it's an honor to be used as a tool for their sexual gratification... and they love it too.
Every time Kuro and Keito fuck Souma they get a little more indulgent. Eventually they can't help themselves, and start using Souma as a willing outlet for every depraved fantasy hidden in their heads.
Kuro and Souma soon discover their shared breeding kink, and Kuro determines there's nowhere more satisfying for him to cum then inside his sweet little junior who wants it so bad. A cum shot is an acceptable way to reward your junior idol for good behavior, right? It must be, if he enjoys it so much... Right?
Kuro ends up conditioned to seek Souma any time he's feeling pent up. Nothing hits for him quite like his sweet little Kanzaki, a dark corner and pulling aside just enough clothing to relieve his problem. (Kuro also enjoys the adrenaline high from public sex, and Souma never turns him down no matter where they are.) Kuro always makes sure to groan about what a good boy he is as he finishes, which has finished Souma too on more than one occassion.
Keito grows to enjoy the power dynamic Souma grants his one and only unit leader. Keito used to dislike being called 'My Lord', he used to see it as childish and silly.
But 'My Lord' hits different the first time Souma says it on his knees - then it stirs something in Keito that he's fought to suppress for the sake of common decency.
Halfway through fucking his junior's mouth, Souma's words are still echoing in Keito's ears. "It's my honor to serve you, my lord." He meant it. He's being so obedient, engaging his warrior's discipline to accept Keito's cock into his mouth without gagging. No matter how deep Keito goes, Souma channels his immense devotion and willpower to remain compliant.
As if he really is honored to be face fucked.
Eventually Keito's decency abandons him, he grabs the base of Souma's ponytail, and starts thrusting into his throat. Souma takes it until there's tears running down his cheeks and a smile around his mouthful of cock. Keito moans and moans like he's lost his mind, then cums so hard his whole body shudders.
He tries to apologize for losing control, but when Souma catches his breath he rasps, "Thank you for all of your guidance, sir."
Keito is still mostly gentle when interacting with his unit mates, but he develops a harsh and intense 'bedroom voice' for when he's in the mood. Keito likes being respected. He likes being in command. And Souma (and Kuro too fwiw) get off on feeding his ego. So why not indulge the mutualism for all their satisfaction? Behind closed doors, he really does become their 'Danna'.
