Not figuring out their do not cross lines ahead of time bites Shiro and Keith in the ass in this fic. You've been warned.
This is the most humiliated he's been in his entire life.
Keith's clenches as the alien pulls out. Trying to keep even a drop from spilling free. That was his instructions for this game. Keep everything the aliens gave him. He would have done it anyways. He can't stand the thought of any of this running down his thighs.
The next alien grabs his hips roughly, spread Keith's cheeks, and shoves what passes for a dick in its species into his hole. The alien sighs, as warm liquid piss pours into his insides. Relieved to finally get his turn with the communal toilet. Keith closes his eyes and tries to focus on his breathing, away from how much is being emptied into him. How little more he can hold before he starts to leak. How the slanted table seems less like it's meant to help him like Shiro said, and more like a trap so when he can't keep it all in anymore it will run downhill to his chest and face.
The alien's dick goes from a torrent to a trickle, then pulls out far too fast. Keith can't clamp down in time to stop some of the piss gushing out. Streaming down to his ball and soft cock before following the table down to his stomach. Keith's eyes sting with the first sign of impending tears. He buries his head in his arms. He won't make the humiliation worse by breaking down in the middle of this.
The next alien hesitates before pushing in. Obviously disgusted by the gross mess he's made of himself. He's no longer just a toilet. He's the gross public toilet that no one wants to touch lest the filth rub off on them. The General paid the alien well though. He gets over his personal cleanliness standards and does his business just like the other two. Keith's bowels hurt, but this time he doesn't leak when the alien pulls out.
There is a moment of silence, where all Keith can do is dig his fingernails into his arms and wonder what else there is left to do to him. Then Shiro speaks, "Very good, you all may leave." There is small commotion as the aliens jump to do as they were told. Keith waits until he hears the door open and close before he raises his head.
Shiro's the only one left in the room. He's watching Keith with an eager gleam in his eye. Drinking up Keith's shame. Just a little longer. Just a little more debasing himself to make Shiro happy, then they can go do something he enjoys instead.
"Come here," Shiro crooks his finger. Keith can feel the loss of gravity's aid as he stands. The heavy liquid trying to force its way past his sphincter muscles. Every step feeling like he's being jarred closer and closer towards disaster.
He doesn't know what he's expecting to happen when he gets to Shiro, but it wasn't for Shiro to put one hand on his lower back and then use the other push on his stomach. There is not enough time to jerk away. The added pressure is all it takes for the piss to win the fight against Keith's muscles and coming rushing out his hole to pour down his legs. He stares at the disgusting mess he's made. Feels the shame at his loss of control bubble up until he feels he might choke on it. Then when he can't take looking at himself one second longer, bursts into tears. Shiro's been watching him with a hungry smile, but his expression quickly morphs to one of alarm with Keith's outburst.
Keith's an ugly crier. His face splotches, snot threatens to run from his nose, but he can't stop. Even as a concerned Shiro reels him and begins to murmur at him, "Don't cry, baby," Shiro pets his face, uses his human hand to rub comfortingly along Keith's side, "Please, don't cry."
He thought, he could do this. He's let Shiro do things to him in the past that he hasn't enjoyed. This should have been the same, but for some reason, the humiliation of this time makes it so so different, "I-I don't want to play this game anymore." Keith chokes out between sobs. Whatever else Shiro had planned for the night, he no longer wants to do. He just needs to stop feeling so disgusting.
Keith goes willingly, when Shiro pulls his head against his shoulder, "Of course, baby. We're done. Nothing more tonight." Shiro kisses his temple, and Keith is filled with a wave of relief. He doesn't stop crying, not yet, but his tears now have more in common with sniffle than sobs, "Lets wash you off, okay? Then I'll draw you a warm bath. Do you want that?"
Keith nods against Shiro, then adds in a whisper, "Thank you."
Shiro stops his soothing. He looks down at him, like there is something he wants to say but doesn't know how. After a moment, he gives up. Giving Keith a quick peck on the lips instead, "Lets get you cleaned up."
These sorts of events are not Shiro and Keith's nightly routines. They tend to do these things about once a month or so.