The next few days felt like some strange sort of persecution. The case wound up depressingly quickly (no mystery about it at all, to Sherlock's crushing disappointment) and thus John found himself saddled with a flatmate who was just a little bit too present. And who seemed determined to make John blush.

He wasn't subtle about it, either - Sherlock was seizing every opportunity possible to demonstrate his missing gag reflex. John sat curled up with his laptop in his armchair and watched out of the corner of his eye as Sherlock deep-throated another spoon, two carrots, a popsicle, a truly impressive length of the curtain rod, and, the most disturbing, a raw zucchini. Each time Sherlock would smirk and look over at John, as if he were expecting applause. And John would studiously avoid eye contact, pretending to be engrossed in his blog. He couldn't hide his immediate reaction to the zucchini, though, and Sherlock pounced on the opportunity to tease him about it.

"You're bright red, you know."

John kept his eyes on his laptop. "I know."

"And yet you think by watching me only in your peripheral vision, I won't notice you staring."

"I'm not staring, Sherlock, I'm trying to write. You persist in showing off."

"Because you like watching." Sherlock wandered over to loom directly next to John's chair, very definitely in his personal space. "You keep imagining what my throat would feel like around your cock."

John snapped his laptop shut but refused to turn around. "Only because you won't leave it alone. Honestly, Sherlock, boundaries. I'll get over it eventually."

"If I wanted you to get over it I would never have mentioned it in the first place." He rested his hip on the arm of the chair, right next to John's shoulder. "I thought it over and I decided I would very much like to perform oral sex on you."

John blinked.

"You're significantly larger than the mean for British males," Sherlock continued. "By a good twenty-five percent. I think it would be an interesting experience."

That snapped John out of his shock and into - not anger, necessarily, but that indefinable annoyance he was getting used to after living with Sherlock for so long. "Please tell me you don't have one of Mycroft's hidden cameras in the bathroom or something."

"Oh, God, no," Sherlock said quickly. "There are things even Mycroft doesn't want to watch. But I've seen you in just your pants a few times and I can extrapolate as well as anyone. You are particularly large, aren't you?"

John knew his blush was getting worse - how exactly does one answer that question? He swallowed and tried to ignore the fact that Sherlock's own cock was less than a foot from his head. "I've never measured," he finally choked out.

Sherlock made a little humming noise. "No matter. Even if your cock is of completely average dimensions, I want to feel it in my mouth. It's been way too long."

"You've done this often?"

He felt Sherlock shrug. "Used to. Haven't since you moved in." Sherlock shifted his weight, and John could feel his gaze on the top of his head. "Before you ask," Sherlock added, "yes, I have been safe about it and yes, I'm clean. I've been no more promiscuous than you have."

Since that wasn't saying very much - John's army days were filled with a long string of one- and two-night stands - John opted to keep his mouth shut.

"So may I?" Sherlock came around the chair to kneel in front of John. He took the laptop from John's slack grip and placed it carefully on the coffee table behind him, then turned back and let his hands drop casually over John's knees. "I know you're not gay, but -"

"-but very few guys, gay or straight, would turn down an offer of a blowjob," John finished. "I'm well aware." He let his gaze rest on Sherlock's upturned face, then drift to where Sherlock's long fingers were stroking him gently through the fabric of his trousers. "You've got the most singularly unromantic way of requesting sex of anyone I've ever met, you know that?"

Sherlock smirked. "So that's a yes?"

John sighed and rolled his head back to stare at the ceiling. "That's a yes, God help me."

"Excellent." Sherlock's fingers started trailing up John's thighs toward his waist. "I have been thinking about this for a while."

John licked his lips, mesmerized by the feeling of the light brushes through the fabric. "How long, exactly?" he asked.

"Mmmm. Since about two months after we moved in together, and I saw you in those ratty cotton Y-fronts. The time I accidentally splashed acid on you and you had to strip down right there in the kitchen."

"So my least sexy pair of pants."

"I wasn't paying attention to the pants; I was observing the bulge beneath them." Sherlock deftly unzipped John's trousers and motioned for him to lift his hips so he could slide them down to John's knees. John was wearing another pair of plain white Y-fronts underneath - not the old ratty ones, thank goodness, but nothing particularly special either. Sherlock was eyeing his pants with the glee he usually reserved for locked-room murders, though. "Christ, this is going to be fantastic. Lift your hips again."

John did, feeling absurdly self-conscious, and then he was sitting in his armchair in just his jumper while a fully-clothed Sherlock grinned at his cock with manic glee. He didn't even need to glance down to know that he was more than half hard already, and growing by the minute.

"Incredible," Sherlock murmured. "If anything, I under-estimated. You are so fucking huge - oh, this is going to be glorious. Significantly above average for girth as well as length."

"Making me a bit self-conscious, here."

"Why?" Sherlock glanced up at his face, then reverently stroked two fingertips down the length of John's cock. "I'm the one with the size kink. If anything, I'm the one who should be embarrassed."

"Yeah, well, I wasn't aware you even knew what sex was until the whole gag reflex thing came up."

Sherlock shot him an incredulous look. "I may not flaunt it, John, but don't you think that would be a rather major thing for me to not know?"

"Oh, like the solar system?"

"Shut up," Sherlock said, and leaned forward to engulf John's cock with his mouth.

And Christ did it feel amazing. John collapsed against the back of the armchair and didn't protest when Sherlock tugged his hips forward a bit more so John was semi-reclining with his cock jutting out obscenely. Sherlock licked gently over the head, then slid his lips all the way down the shaft again.

"Fuck."

Sherlock pulled off slowly, allowing the suction to build until it made a little popping noise when he slid free. "This won't work - the angle is all wrong. Come to bed."

John obeyed with a stunning lack of reservations. Sherlock led him by the hand into his room, letting go only to smooth out his bedspread over the unmade sheets and to gently shove John onto it.

"Sit up with your back against the headboard, legs apart."

John took the opportunity to shuck his jumper - surreal as this all was, it was one step too far for him to still be wearing it while Sherlock was sucking him off. Sherlock was still completely clothed, right down to his shiny expensive shoes, but he'd surely undress when he was ready . . .

Sherlock pounced on him like an oversized cat the moment John was positioned properly. He prowled up the length of the mattress until he was on all fours between John's legs and was just breathing on his cock. If John hadn't been fully hard already, he would have gotten that way rather quickly. Sherlock looked up at John's face with a pure feral grin - and then he attacked.

John felt like he had just touched an electric fence - one moment he was staring into his mad flatmate's eyes, still feeling slightly stunned at the direction his life had taken, and the next moment Sherlock's mouth was all the way up against the base of his cock and fuck John could feel the ring of Sherlock's throat around him as he worked John's length deeper. Sherlock pulled off with an obscene slurp and sucked in a deep breath. "Phenomenal," he growled quietly, vibrations from his voice rumbling through John's skin. "You're so thick - I have to stretch to fit all of you in. It's incredible." And he worked his way down again, using his tongue for added sensation as he slowly sank down inch by inch until John was moaning and his hips were twitching and Sherlock had to restrain him to keep him from bucking forward too forcefully.

"Slow," he gasped when he came up for air again. "Let me savor you, John."

But John didn't want to be savored, and he would have said so if his voice had been working properly. He wanted that deliciously moist heat around him again and again, sliding back and forth until he couldn't hold back anymore. He wanted to come in Sherlock's mouth, pouring his come straight down Sherlock's throat so Sherlock wouldn't have a chance to draw back or spit it out. He wanted to wrap his fingers in Sherlock's curls and fuck himself with those talented lips and tongue and bruise Sherlock's goddamned uvula. Three days ago John hadn't known he would want this, but now he wanted it more than fucking breathing.

And Sherlock, damn his perceptiveness, seemed to realize it. He licked his lips slowly, eyes stuttering back and forth from John's face to his cock, and then seemed to make a decision. And fitted his mouth and throat over John tigher than a fucking glove.

"Fuck, Sherlock, I can't - I just -"

Sherlock hummed around him, ratcheting the tension inside John even higher. It was a vaguely encouraging hum, accentuated by how Sherlock's hand had just moved from tracing the inside of John's thigh and now was massaging his bollocks in time with Sherlock's tongue movements against John's shaft. And suddenly John couldn't take anymore, and the world went fuzzy a bit around the edges and he was pouring his come into Sherlock exactly like he had been dreaming about. Sherlock hummed again, a happy noise, and waited until John's body had stopped jerking before carefully pulling away from his cock and crawling up and laying his head on John's chest.

"You're still hard," John observed once he got his breath back and the world had stopped spinning.

Sherlock shifted slightly and pressed a kiss to John's collarbone. "Give me your hand and you can help."

John obligingly let his hand flop, palm-up, on his stomach. Sherlock yanked down his trousers and pants with no sign of his earlier finesse and grabbed John's wrist to press his hand over his own straining erection. John let his fingers curl posessively over Sherlock's warm skin. Sherlock covered John's hand with his own and set up a punishing rhythm - before long, he was groaning and then spilling over their joined hands and eventually slumped back, as boneless as John felt, against John's shoulder once again.

"So." John said quietly. "That happened."

"Finally," Sherlock mumbled.

John tried to twist his head a bit so he could see Sherlock's face, but all he got was a mouthful of dark curls. "You really - that was okay?"

Sherlock tightened the arm thrown over John's ribs and burrowed deeper against John's side. "Knew you'd be amazing. Didn't want to push."

" . . . because you didn't want to scare me away."

John felt Sherlock nod.

"I'm not leaving you, Sherlock. When are you going to realize that?"

Sherlock made a low, sleepy noise. "Everyone leaves. Eventually. Don't want to let you go."

John wrapped his free arm around Sherlock's shoulders and pressed a kiss into his hair. "I'm not going anywhere. You don't have to hide from me."

"I won't change. Can't."

"I don't want you to." John nuzzled another kiss into Sherlock's curls. "I'm happy just the way we are, strange experiments and all. Although the sex will definitely be a plus."

"Mmmmm."

"Sherlock?"

But there was no answer, because Sherlock was asleep. John let his cheek rest against the top of Sherlock's head and eventually drifted off.