John's brain was more or less completely shut down, which meant he was still standing frozen in the kitchen doorway when Sherlock gave a triumphant "aha!" and extracted two of the bags from the pile.

"You're still dressed," Sherlock announced with disappointment in his voice.

". . . Yeah."

Sherlock made an exasperated sound and launched himself into his armchair. "Fine, then, would it help if I walked you through my deduction?" He spoke rapidly, not giving John a chance to object. "Point one: we've spent quite a bit of time together, in various circumstances, and I've seen you nude before. Never in a sexual context, I'll grant you, but you do have quite nice genitals, aesthetically speaking, and you're not ashamed of them. Therefore your discomfort stems from me seeing them in this context, in a sexual context, although of course it will be more sexual for you than for me. That's plebeian but relatively common; many people experience anxiety in sexual situations. I expected better of you, John - so depressingly ordinary. There's no need."

He rubbed his finger over his lips thoughtfully. "Point number two: your current sex life is less than satisfactory. You do have a higher-than-average success rate acquiring physical intimacy on your first and second dates, which you find useful - I'm not going to go into all the things I notice when you come back afterward which tell me you had a successful 'pull' but I assure you there are several - but you inevitably fail to return from your dates with what is euphemistically termed a 'glow.' Satisfactory sex, then, but never mind-blowing. Point three: you do often have the 'glow' after watching porn in your room - yes, of course I know - and point number four, an examination of your browsing history reveals a definite lean toward kinky activities, specifically domination/submission, specifically humiliation play. Inevitably a male in the submissive role, although you seem to have less preference for the gender of the dominant - very liberal-minded of you, actually, but it reflects your non-polarized standing on the Kinsey scale so it's unsurprising. How am I doing so far?"

John blinked. "Um."

"Not wrong."

Damn well spot-on. "No."

Sherlock smiled. "Well then. Do I need a point five? Point number five: you've achieved a significant erection already, just standing there, thinking about me directing you in a sexual way. You try very hard not to think of me and sex in the same mental sentence - what you quaintly deem 'common courtesy' for flatmates - although it honestly doesn't offend me one way or the other. I don't mind you wanking over thoughts of me, as long as it doesn't affect The Work. In that vein, this experiment ought to provide a significant amount of material for that purpose. I can't offer you a 'relationship' - I'm rarely interested in the actual practice of sex - but I'm perfectly happy to provide you with sexual release whenever you require it."

John blinked. "Are you - are you offering a 'friends with benefits' thing to me?"

Sherlock's lips pursed together. "As much as I despise that term, I suppose it's an accurate summary. And you're still wearing clothes. Take them off, please."

Do I want this? It was a stupid question - of course he wanted this, would have been grateful for any scrap of attention Sherlock gave him - but John still took a full five seconds to think it over before reaching down to unbutton his trousers.

"Finally," Sherlock grumbled. "All the way off; let me see you."

Even though John knew Sherlock wasn't asking because he was aroused - he still sat there calm as could be - he flushed a bit as he toed off his shoes and yanked the trousers down past his ankles and set them carefully over the back of the closest kitchen chair. Socks next, including that awkward wobble he always ended up doing before needing to grab something for balance. He took a deep breath, shucked his shirt, and then he was standing there in the kitchen in just his pants with a massive hard-on.

"All of them, John," Sherlock warned.

John closed his eyes and eased his pants off, too. When he opened them again, Sherlock was standing and staring with a rapt expression.

"Phenomenal," Sherlock said quietly. He took a few steps closer. "I assume you have no objections to touch?"

John swallowed and shook his head.

Sherlock crowded into his personal space, attention fixed solely on John's cock. Which was very definitely interested in whatever was going on. Sherlock reached out and wrapped his hand around it, giving it a gentle squeeze, and John's knees went suddenly wobbly. Fuck.

"Data," Sherlock said quietly, his voice a low rumble. "An approximation of size and tumescence."

"Ah." The word came out strangely strangled.

Sherlock withdrew abruptly, whirling around and going to pick up the bag he had dropped on the floor near his armchair. "Come on over here," he said absently as he dug in it. Something clinked.

John came closer. And then stopped, rooted to the floor, when Sherlock pulled out a disassembled spreader bar.

"So you know what this is," Sherlock said. He deftly slid the pieces into place, pinning the hollow center tube at its shortest possible length between the cuffs on either end. "Here." He dropped to his knees in front of John, leaning forward to wrap one of the cuffs around John's ankle, and John went lightheaded the moment he realized how close that put Sherlock's mouth to his naked cock. Sherlock didn't seem to notice, though, just nudged John's other leg a bit farther out and affixed the other cuff. He pulled two tiny padlocks out of his pocket, snapped the cuffs shut, and sat back on his heels. "That oka- oh." His gaze lit on John's erection. "You like the spreader bar, I take it."

John swallowed.

And Sherlock's expression changed. "Not the spreader bar. Or rather, you don't dislike it, but you- ah. When I leaned in, you liked that?" He palmed John's cock again, squeezing gently. "Having me on my knees in front of you makes your erection firmer. I'll have to remember that."

John whimpered. Whether it was because of Sherlock's touch or because Sherlock withdrew his hand, he couldn't say.

But Sherlock was already standing up and spinning around in place, eyes darting around the room. "Notebooknotebooknotebooknoteb- right." He grabbed it and scribbled rapidly for a moment. Recording John's measurements, presumably. "I'll stop if you want me to, you know," he said casually. "Your limits are part of the experiment, too."

"It's - yeah. It's okay." John swallowed again. "I mean, weird as fuck, but if that bothered me, I wouldn't still be living here."

"Mmmm." Sherlock scrawled a final line, then whirled again, clearly in the throes of one of his manic-crazy-experiment moods. "Yes. Right. Humbler next."

That wasn't something John was familiar with, but it sounded . . . yeah, okay, it sounded a lot more promising than it should have. And, when Sherlock pulled it out of the bag, it didn't look all that threatening - a slightly curved black stick the size of Sherlock's forearm.

"You've never used this one," Sherlock observed.

"Lot of things in that shop I've never used," John countered. "Want to tell me what it is, before you try it out on me?"

Sherlock shrugged and pointed toward the arm of John's chair. "Turn around, hands there. Lean over."

John rotated a hundred and eighty degrees the best he could with his feet a fixed width apart. He was just barely able to brush the armchair with his fingertips without leaning.

"Further." Sherlock tossed the humbler down on the seat of the chair, shifted around to stand behind John, and grasped John's hips in both hands. A swift tug had John grabbing wildly for the chair's arm to keep his balance, since his feet couldn't move fast enough. "There, like that, ninety degrees is probably close enough." He started twisting something on either end of the toy. "A humbler just keeps you bent over - it does nothing on its own unless you attempt to stand."

"How does it - oh." John broke off the question. Sherlock had unscrewed something, and it turned out what he had assumed was one piece of plastic with a hole in the middle was actually two thinner sticks, stuck together.

"Essentially stocks for your testacles," Sherlock said calmly. "Hold still."

John tried, but the feel of Sherlock's hands brusquely brushing over his bollocks and then tugging inspired a great deal of reaction from John's nervous system. Most of it good, in the oh god oh god MORE vein, but also a shot of embarrassment which quickly transformed into lust. Most men wouldn't be turned on by this, John knew. Most men would have been cursing up a storm by now and would absolutely not be practically quivering with anticipation over what their presumably-asexual very-definitely-male flatmate might want to do next to them. Most would probably be just about ready to deck him-

"Ah!" John nearly doubled over at the feeling of Sherlock stretching him, tugging his bollocks backwards and then the cool bite of the plastic around his sac and a pause while Sherlock screwed something back in, and then a gentle pressure against the backs of his thighs where the ends of the humbler dug into his skin.

"Comfortable?" Sherlock asked from behind him.

John shifted his weight and assessed. Sherlock hadn't lied - the humbler didn't hurt. As long as he stayed bent over like this, at least. He started to straighten, but was brought up short by the painful pressure on his balls. Right, so he'd be staying folded over like this. Christ, that meant Sherlock was standing right there in the perfect position to see his bare arse displayed like a . . . his brain couldn't supply a proper metaphor, but it was something embarrassing. And hot. Again. John dragged in a shaky breath.

"Hold it right like that - one second." There was a rustling and then footsteps behind him. Sherlock wandering off into the kitchen. And then coming back with something-

Something cool pressed against the very tip of his cock. John glanced down just in time to see Sherlock remove the microscope slide, tilt it to better catch the light, then touch a second slide to the damp drop of pre-come still leaking out of John's erection.

"Comparison," Sherlock explained. "I don't have a strong enough microscope to examine the minute details, but I should be able to get a general idea."

"Fuck." John swallowed down the moan that almost escaped his throat. Apparently Sherlock was right about his humiliation kink, too - never in a million years would he have thought he'd be so bloody turned on by Sherlock being completely indifferent to his state, but if the Sherlock left the room right now, he'd probably wank himself half blind before the detective got back, consequences be damned.

"Last thing," Sherlock said, and plucked a smaller bag off the top of the pile. Knew exactly what he was looking for, apparently. "I took it out of the packaging and cleaned it and put batteries in it already for you, so you don't have to worry about that. I assume the black one is acceptable?"

Since color played very little part in John's recollection of butt plugs at the store, he kept his mouth shut. That lasted up until Sherlock drew up behind him, slid one hand possessively over his arse, and then pressed. There was the slide of something (already lubed, it felt like) gliding inside him, long and thin. John would have said a finger, but it was too smooth and cool and oh, there was little dip and then a flared base at the end. Sherlock drew back to the side, where John could see him, stuck his hands in his pockets, and surveyed John critically.

"How does it feel? I'm honestly curious."

John licked his lips and sucked in a breath. "Odd? Smaller than I expected, and- ungh."

Sherlock withdrew his hand from his pocket and held up a small black remote control with round silver buttons. "That's the low setting," he said with a smirk on his face.

Oh god oh god oh god. John closed his eyes and let his head hang loose. Sherlock with the remote, controlling that maddening buzzing against his prostate, watching him with that dispassionate look. It absolutely fucking shouldn't have been such a turn-on, it shouldn't, but ChristfuckshitdamnbloodyHELL it was. Oh, it so totally was. John just knew if he actually looked down right now, his cock would be leaking like a cheap faucet and practically purple with how hard he was. And Sherlock could see, would know, of course he'd notice, and somehow that just made it worse. Which just made John harder.

"Fascinating," Sherlock murmured. "I suspect the tension the humbler is putting on your testicles may be helping delay orgasm. We'll have to run some comparison studies later."

John squeezed his eyes shut tighter and panted. His thighs were starting to smart from holding his bent-over position, but the burn just added to the whole experience.

All of a sudden, the vibrations stopped. Sherlock laid a hand on John's bare hip, gently pressing him toward the kitchen. "Best put the groceries away before the frozen things melt."

John twisted his head to stare at his flatmate.

And Sherlock shrugged. "Not my fault you bought so much," he said calmly.

It kind of was, if John had been willing to admit it in that many words, but he wasn't so he kept his mouth shut.

Sherlock stared at him for a minute longer, then growled low in his throat. (A sound that went straight to John's cock, but then again, pretty much everything this evening had.) "Fine," Sherlock grumbled, and pushed past John to go into the kitchen. John could just make out Sherlock in his peripheral vision - he was moving all the Tesco's bags from the counter to the floor. "Now you can reach," he said. "Although I guess I forgot to tell you we're out of eggs."

Eggs. Sherlock wanted to talk about sodding eggs.

"I mean, if you want to," Sherlock added. There was an uncomfortable quality in his voice John rarely heard - it only came out when Sherlock was unsure of his reception and it was about a subject that mattered to him. It took a moment, but John put the pieces together: Sherlock was nervous that he'd pushed John too far. That meant he knew this was a bit much for just flatmates, which meant that despite his protestations of asexuality, he genuinely cared whether John was enjoying himself or not. John set aside the question of whether Sherlock got off on watching him - sexual or not, he was deriving pleasure from setting up this experiment, cocked-up as it was, and John liked seeing Sherlock happy. It was as simple as that.

And, therefore, so was John's answer. He lifted one foot cautiously and shuffled forward. He had to hold the arm of the chair and then the doorway for balance, bent over so far and with his feet stuck an awkward more-than-shoulder-width apart, but he slowly made his way into the kitchen and rummaged through the first bag.

"Going to have to hand you anything that goes into the higher cupboards," he commented.

"That's fine."

Sherlock waited until John had the milk safely in the refrigerator before turning on the vibrator again. It was a wise move - John jerked at the sudden sensation, doubled over at the immediate and intense pain in his bollocks, and dropped the package of biscuits he was holding. Sherlock scooped the package off the floor and shook it once before depositing it in the cupboard.

"Broken, but still edible. Tell me - good? Bad? Stop? More?"

John braced his elbows on his knees and allowed himself a second to just breathe. "Standing up fucking hurts," he finally said.

"How about the plug?" Sherlock hit one of the buttons before John could reply, and the vibrations intensified. John couldn't manage a real answer, one with words, but he let out a long moan.

"That's a good moan, right?"

John nodded frantically.

"Excellent. Oh, there's cheese in that one on the left - best get that in the fridge as well."

Somehow, John wasn't entirely sure how, he worked his way through the entire stash of groceries. Sherlock lounged against the kitchen table and played with the remote while he worked. Sometimes he turned it off entirely, but other times he surprised John with sudden vibrations while John was in various poses - leaning all the way down to dig something out of the bag, or braced against the counter for balance, or reaching as high as he could within the confines of the humbler to put the tea away. John nearly chinned himself on the counter at that last one.

"You're making the most amazing facial expressions, you know," Sherlock said quietly.

John licked his lips and braced himself through a particularly devilish round of vibrations, which Sherlock waited to cue until John was bent nearly double and the vibrator was pressed extra-snugly to his his prostate. "Can't see them," he panted.

"Makes me want to take pictures to analyze later."

John shook his head as hard as he could. "No pictures."

"I know," Sherlock said in the same quiet voice. "I do understand. But just think, John - I could go get my phone and take a picture of you like this, rock-hard and dripping and flushed all over, even your arse, clenched around the flared base of the vibrator and with your scrotum pulled back so far . . . it would make a fantastic shot. I could keep it forever, pull it out whenever I wanted."

Fuck. John could see it, could absolutely see it in his mind's eye - how he looked right now to Sherlock, quivering and subservient and needy. He was mortified and so bloody turned on he couldn't see straight. And then Sherlock hit something on his remote again, and the vibrator buzzed to life even faster than before, and John literally screamed and his knees gave out under him and fuck, he was coming so hard he blacked out.

When he opened his eyes again, Sherlock was scooping up a sample of his come with one long fingertip and wiping it on another microscope slide. He did a second one - for backup, presumably- then grabbed a paper towel off the roll on the counter and offered it to John. While John dabbed at the mess he'd made, Sherlock crouched on the floor behind him and unscrewed the humbler and extracted the vibrator (now off, thank goodness).

Finally able to straighten properly, John rolled to his back and just let himself lie there on the cool floor. Sherlock extracted a tiny key from his pocket and unlocked the cuffs on the spreader bar while John just watched with what he knew had to be a dazed expression. Sherlock massaged John's ankles between his palms, each in turn, then knelt and offered John a hand up. They ended up sitting on the floor, backs against the cupboard doors, both just staring at the legs of the kitchen table.

"So," Sherlock finally said.

"Yeah."

"Was that . . . too weird?"

John took a moment to word his answer. "Not - not how you're probably thinking," he finally said. "I mean, yeah, that whole thing was embarrassing, but that was kind of the point, wasn't it?"

Sherlock nodded once, silently, a question on his face. Still not getting it.

John sighed. "It's just - you're asexual. And I'm not actually gay."

"And?"

"And I just had a bloody phenomenal orgasm - hands-free orgasm - as part of an experiment. Which you didn't get anything out of."

"Ah." Sherlock's fingers laced together. Fidgeting. (Sherlock never fidgeted.) "You . . . won't want to do any follow-up, then?"

John leaned sideways, nudging Sherlock's shoulder with his own. "Don't you fucking even start. I did say it was a phenomenal orgasm, didn't I?" He snorted. "Plus, you've still got a huge pile of bags to work through."

"Ah." Noticeably more cheerful this time. "I wanted to - but I was afraid you'd-"

"I'm not leaving, Sherlock." John turned and tugged on Sherlock's arm, so they were actually facing each other. "I know you aren't offering a 'relationship,' whatever that actually means, but I love living with you and following you into mad schemes and if I get off on it sometimes - literally, like tonight - then that's good enough for me. I'll extend the same offer, but even if you're not interested in sex, this - just this - is fine. Good." He felt his expression dissolve into a grin. "Bloody excellent, in point of fact."

Sherlock's answering grin bordered on manic. "Want to see what else I got?"

John indicated toward Sherlock's microscope with a jerk of his head. "Surprise me tomorrow - right now, I think you've got results to record and samples to analyze."

Yeah, this will work.