Pretext: At age 18, all male citizens are screened for beta characteristics (for their own good, according to this alternate society/reality).
"Alright, almost done sweetie. Now please bend over the bench and we'll get you strapped in," said the pretty technician.
"Oh okay...um should I put my underwear back on?" Tim asked timidly since the hospital gown he had on didn't have much covering in the rear.
"No, of course not, that would just get in the way," she answered looking at him like his question was the silliest thing she'd ever heard.
Tim swallowed and steeled his nerves, reminding himself that this was all standard procedure that everyone had to go through and there was no reason to be embarrassed. Still, as he bent over the padded leather bench, which was inclined so that his head was below the level of his hips, he felt his skin flush with humiliation as the gown fell open, baring his pale buttocks to the world.
"All the way down now, sweetheart" the tech said as she gently but firmly pressed down on his lower back so that his body pressed tightly against the leather. She secured him to the bench with three thick leather straps: one across the back of his head pushing his face firmly through the little oval like they have on massage tables, one across his upper back at a level that conjured a bra strap in his imagination, and one just above his hips near the end of the bench.
It had been an interesting day to say the least. Although the details of the beta screening that all boys went through when they reached adulthood were not public, Tim had expected that the screening might have some invasive aspects. After all, betas were almost by definition addicted to receptive anal intercourse, and the imagination could dream up many ways to test for that.
The screening procedure had begun with a written test. Only a few of the questions had been overly sexual. Most were scenarios about how to respond to confrontations or challenges. Even though they had told him to be honest and that it was impossible to fool the test, Tim had selected the answers he thought sounded the most alpha.
The next phase had involved strapping him into what looked like a gynecologist's exam chair with his feet up in stirrups. First they placed a VR headset on him and told him that this part of the screening would test his response to different types of pornography. All he had to do was relax and watch the videos in the headset. Before the videos started, they had put all kinds of sensors on him. A sensor around his wrist to measure his heart rate and sweat production, sensors on his temples to measure god knows what, a couple that gently clamped over his nipples. When they attached the engorgement sensor, a series of velcro rings strapped along the length of his penis, he had figured that would be the end. But then a gloved hand had smeared thick vaseline around his anus and a thin, short butt plug sensor had been eased into his rectum.
The first videos had been relatively vanilla, heterosexual porn. As Tim watched and became aroused, he noticed that the straps around his penis felt tighter as he became erect. He thought that the nipple sensors felt a little tighter and the butt plug sensor a little bigger too, but he wasn't sure.
Next, there had been some generic nature shots of waterfalls, forests, etc., which Tim figured were like palate cleansers in between courses of different types of erotic imagery. When the screen shifted back to porn, it featured a curvy girl bending over and spreading her cheeks, while a muscular man worked his dick into her tight asshole. Tim felt his own asshole contract around the plug sensor in solidarity, as the other sensors started feeling tight again as well.
He'd had a special fascination with anal sex ever since he'd discovered online porn. Lesbian anal bdsm strap-on porn was his favorite, but in truth anything involving a thick cock sliding between feminine buttocks hooked him.
Even when the next nature scene ended, he was still somewhat aroused from the anal sex scenes beforehand. Then gay porn began to stream through his headset. He was somewhat relieved to feel his erection dying down as he watched two men making out.
The next section brought his arousal back to its peak as he watched an overweight, fully dressed woman peg her skinny male lover's ass. He thought he might cum when they showed an athletic guy butt fucking a transexual woman from behind. It wasn't just the anal sex that got him going, but the domination as the man pulled on her long hair, forcing her to arch her back more, pushing her little tits forward and her soft cushy ass back into his hard thrusts. Tim didn't realize it, but he was rhythmically squeezing his asshole around the plug as he watched.
But then the scene changed to a slow pan of a mountain landscape. And so it continued, clips of so many types of smut that Tim lost count. Some of them seemed repetitive, but he wondered if there were subtle differences helping them to map his arousal.
By the time the screen went black, he had completely lost track of time. He felt exhausted, emotionally and physically as the technician removed the sensors from his body. Tim had absently wondered if this was the end of the test, but then the technician had told him to bend over the bench for the next phase.
Now as he lay face down with most of his weight on his chest, his back arched by the shape of the bench, lifting his butt as high as possible while keeping him bent at the hips, he suspected that there was going to be some sort of anal test. He wasn't really worried. Tim had tried sticking a sharpie marker up his ass years ago after watching the apparent enjoyment of so many pornstars upon anal penetration. It hadn't turned him on at all, and he'd felt foolish for even trying it. He wondered how he had done on the written and porn parts of the test, but everyone knew that betas were hopelessly submissive sexual deviants who could think of little besides their next orgasm, so he felt confident that his performance so far in no way resembled that.
The technician helped guide his knees to the pads on each side of the bench. He was surprised how close to the head-end of the bench they were. He almost wasn't flexible enough to bring his knees that high. The position made Tim feel lewd, almost slutty.
The technician told him that he was welcome to hold on to the rubber handles next to his head. She then went back around behind him and donned fresh latex exam gloves. Tim felt her gloved hands glide slowly over his buttocks. The touch felt unprofessional to Tim, but he didn't say anything.
"Got a bit of a bubble butt, don't you?" she asked him as she continued to assess/fondle? his butt cheeks.
He felt his cock twitch and his cheeks blush with mortification. "Um...I play basketball sometimes," Tim offered as an explanation for his rather pronounced derriere. He just wanted to keep this conversation as non-sexual as possible.
"I bet you do," she said.
Just as Tim was wondering what the hell that meant, he felt something cold and wet being dripped into the crack of his ass. He instinctively tried to raise his head to look back, but obviously the leather strap around his head kept him firmly pressed down.