They called it endurance testing, and they conducted it with efficiency, if nothing else. Shiro woke to find himself already blinded, gagged, and bound at wrist, calf, and thigh. A familiar wetness trickled out of his ass.
He kicked out at once, desperate and bucking, but there was something stiff and inflexible holding him, running from ankle to wrist to throat. The force of his own kick had tightened the rope around his neck, and as he lay gasping for air, a Galra technician’s gloved hand came down hard on his ass, impersonal as if slapping a piece of equipment that had failed to work properly. The force of the blow made him flinch. He could feel his buttocks glowing warm where he had been hit, but Shiro forced himself to stay still. It would hurt more if he struggled, and after that first terrible time, he had resolved to keep himself as undamaged as possible if he was ever to manage an escape.
The gloved hands palmed at his ass, opening him up to the cool lab air. Shiro could feel, for several agonizing seconds, the steady flow of lubricant sliding down his crack, wetting his thighs. The harsh rasp of his own breathing filled his ears: he sounded like a frightened animal.
He had tried to be ready for it, tried to convince his body to take it easily, but the invasion, when it came, was far too sudden. Slick cold plasteel slid into him without warning, and Shiro cried out through the gag.
It was huge, far larger than anything they had tried on him before, and despite all he had told himself earlier, Shiro could not help but struggle. He would die, he thought clearly, through his panic; he would die if they left that in him. He writhed, trying desperately for purchase on the bonds holding him, but with every contortion the thing inside him only pressed ever deeper against his insides. A hard yank to the rope around his neck left him seeing stars inside the darkness of his blindfold.
He collapsed to the table, struggling for breath. It was all he could do; within only a few seconds, the thing had seemed to sap away all his strength. It was too big, too stiff, pressing against all of him in ways that felt fundamentally wrong. A moment later, when it had become as warm as his own body, it began to pulse.
Shiro screamed, forgetting there was anyone at all there to hear him, much less a room full of scientists taking notes. There was too much sensation at once, a pure overload into his synapses. Every nerve was straining. The human body was not meant to take this much. Shiro felt certain of that, as much as he could hold on to any single thought: he was going to die.
At that moment it began to vibrate twice as hard. And then a moment after that, twice as hard again.
His blindfold and gag were both growing wet, but Shiro had no more energy to scream. His entire body was pulsing around the thing inside him. Pain—and one burning, shameful strand of pleasure—chased through his veins. Worst of all, his cock was growing hard.
He was furious at himself for enjoying this, at his body for allowing this violation, but his hands, as heedless as his cock, were reaching, straining against the rope. Shiro could not know whether to feel resentful or grateful when he could not reach. He didn’t want to soil himself, even if the cries coming out from behind his gag were no longer purely of pain. But Shiro could not deny the mounting wave of pressure that was building inside him. The vibrator purred against the secret, pleasurable spot, and Shiro let out a noise that could only be a moan, as wanton to his ears as he felt making it. Untouched, he came over the laboratory table, shaking as the orgasm rolled through him.
Afterwards he collapsed, shuddering with both sensation and disgust. The machine continued its attentions, unthinking and relentless. Only a little while later, his cock began to feel hard again.
Shiro curled on his side, and waited for the hours to pass.
They had never left him for this long before. Shiro had forced himself to count seconds, and then restart whenever another frightening, unwanted orgasm ripped through him and scattered his thoughts. He had besides this a spacer’s sense of time, was used to relying only on his body clock rather than what he might see or feel. It had saved his sanity more than once, during this captivity.
He raised his cheek from the table, now sticky with his own come. He could sense movements around him, but none of the Galra scientists were coming closer. Cowards, he thought bitterly, as the tears ran freely down his face, mixing with the drying come splattered there. The vibrator was a ceaseless agony inside him, pumping pleasure through his traitorous body. Shiro wanted, with all his heart, for it to stop.
And then, as if reading his mind, it did.
Shiro took a sharp, quick breath, hope rising sharply within him. Too sharply. All at once, the vibrator roared back into life, more intense than it had ever had before, sudden enough that Shiro arched his back in shock, unable to speak or cry out. He came instantly, hard and fast and nearly painful. He could not seem to think. The sudden shock had unlocked something within his body, something that hungered for more. It did not want the mechanical workings of the vibrator, but something that could move and stroke and fuck him.
By the end of it he was on elbows and knees, hips bucking back into the air, trying to press it harder inside him.
It was almost a relief when the experiment was ended. The vibrator was pulled out, and something much more organic slid into its place.