((For the record, I spent a day staring at this prompt on my desktop, trying to figure out how in the hell I was going to get them in costumes. And then my brain decided to tinker with the idea, and this is the result. Sorry, not sorry…))

Day Seven – Cosplay

"Come on, Sherlock, please? For me?"

"I don't understand why you want me to wear this…thing."

"It's a joke, all right?"

"But it's mocking everything I do. Everything you do, for goodness' sake!"

"Sherlock…" John ran his hands through his hair. "It's just for a party. One night, all right?"

Sherlock sneered at the costume hanging on the back of the sitting room door, wrapping his dressing gown tighter around himself. John stood next to him, his arms crossed over his chest. All right, fine, so he didn't like the idea of dressing up as a stodgy Victorian doctor either, but at least he was willing to go with the spirit of the thing. Lestrade had invited them to a costume party, a sort of "welcome to the New Year" thing after the headaches the real New Year always brought the police department. The theme was "the old-fashioned version of your real job". That was causing some trouble, since there wasn't such a thing as consulting detective back in the old days, so John had improvised.

John tucked his hands into his waistcoat, adjusting it with a "harrumph". Sherlock glanced sideways at him, and the corner of his mouth twitched. "You look ridiculous," the detective said.

"I know," John said, adjusting the watch chain he'd had Sherlock "borrow" from his brother.

"I like it anyway." Sherlock sounded perplexed. "Why do I like it?"

"Haven't the foggiest," John shrugged. "Because you're not used to seeing me in anything but my jumpers and jeans?"

Sherlock turned to look at him, his hands coming up to press together under his chin as he scrutinized John from top to toe. "I don't think so," he said at last. "Though I think it has something to do with your usual attire. These clothes suit you, actually fit you."

"Hey!" John protested. "I like my jumpers!"

"Preference has nothing to do with it," Sherlock said, waving a hand impatiently. "Your jumpers are loose and unbecoming. A well-fitted three-piece suit accents the muscles you've retained since your return from Afghanistan, and your well-shaped body."

John blinked rapidly. "…What?" he asked, his voice suddenly raspy. He cleared his throat quickly and tried again. "Well-shaped body?"

Sherlock gave him another "I'm being patient because you're being slow" look, one of the few looks that still made John want to punch his flatmate after all this time. "Biologically speaking, you are ideally shaped for procreation. Your features are symmetrical, you're a bit short, but you make up for the height deficit by having everything in good proportion. Well, I say everything, but I can't be completely sure, since you've never let me see you naked…"

John choked, swallowing a mouthful of spit down the wrong tube. "Sherlock Holmes!" he exclaimed.

"What? You don't have anything to be ashamed of." Sherlock smiled, that slow dangerous smirk he got when he was about to do something monumentally stupid. "I propose a compromise."

"Um…what sort of compromise?" John knew better by now than to agree to anything Sherlock said without checking the fine print.

"You let me see you. All of you. And I'll wear your stupid detective costume and be downright sweet to everyone at the party." He considered that last point for a second. "Unless Anderson and Donovan are going to be there, I won't be sweet to them. But I'll be civil, and that's almost as good considering it's them…"

"Sherlock," John said, raising his voice a bit to cut Sherlock off. "Let's go back to that earlier point, shall we? You want me to strip naked? Why?"

Sherlock's eyes flicked off to the left, probably one of the most obvious liar signs John had ever seen in his life. "Curiosity," he said.

"Want to try the truth this time?"

One of Sherlock's dark eyebrows went up in an expression that looked scarily close to respect. "Not bad," he murmured. "Truth? I am curious, about your body. About your scar, any freckles or moles you might have…you, John." One hand came up to touch the tags Sherlock wore under his shirt at all times, and John made the mental connection.

"Oh," he said quietly, blushing all the way to the roots of his hair. "Sweet, is it? You'll actually be sweet?"

"As honey. Or you can exact some horrible form of revenge on me."

John smiled and leaned closer to Sherlock. "I'll hold you to that," he murmured, intrigued by the tiny shiver that ran through Sherlock's body. "I'll be right back, then."

"What?" Sherlock actually looked slightly panicked as John started to walk out of the room.

"Not comfortable with an actual strip-tease, Sherlock. You want to see me naked, fine, but on my terms."

Sherlock settled back a little, relaxing just a hair. "Oh. By all means, then, carry on."

Smiling and shaking his head, John walked up the stairs to his room and closed the door. A silly precaution, really, since he was about to be bare-arsed naked in front of his flatmate, and dear God, what was he doing? He glanced down at his left hand and sighed. The shaking might stop when he was in a genuinely life-or-death stressful situation, but right at the moment, it was shaking like a leaf.

John took a deep breath and looked at his reflection in the dresser mirror as he began undoing the nice clothes, setting each piece neatly on his bed as he took it off. The Army didn't leave much room for bashfulness, so he was relatively comfortable with his body. All right, so there were things he didn't like. He was in good shape from chasing all over London with Sherlock, but he still had a bit of a belly he couldn't quite shed, and of course, there was the scar. He leaned closer to the mirror, acknowledging that imperfection. It had healed rather nicely over the last year, turning into a pale divot in his skin. He didn't have to turn to see the exit wound; that was rather messier than the entrance wound.

Kicking off his shoes, John shed his trousers and his pants, looking himself over nervously before he grabbed his dressing gown and wrapped it around himself as he headed down the stairs to the sitting room.

Sherlock was sitting bolt upright in his chair, tapping his fingers to a rhythm only he could hear as he stared at the stairs, waiting for John to appear. As soon as John's bare foot touched the landing, Sherlock was out of his chair like a shot, his hands pressing together under his chin as he approached John.

"Ah, ah," John warned, lifting a hand to stop Sherlock. "Close your eyes, all right?"

"John…" Sherlock sighed, tipping his head to the side as he stopped in his tracks. "It's not like you have anything I don't."

"Unless you got shot in the shoulder and didn't tell me, I beg to differ," John replied dryly.

"Really?" Sherlock looked John up and down. "That's what makes you shy enough to come down in your dressing gown? Not your genitals or anything like that?"

John shrugged. "You're a guy too. Like you said, we have the same stuff. And I was in the Army for ten years; you learn not to be shy pretty quickly." Except in situations that might turn toward the sexual, but he carefully didn't mention that. He was too unsure of his footing to say anything about that yet. "Now. Close your eyes, or I go back upstairs and get dressed again."

"Fine," Sherlock sighed, but a grin was pulling at the corners of his mouth as he closed his eyes. Just to be sure, John walked behind Sherlock before taking a deep breath and letting his dressing gown drop away. He noticed that Sherlock's spine got straighter as the cloth rustled, and he wondered what exactly was going through that amazing mind.

"All right," John said, folding the dressing gown over the back of his armchair. "You can turn around now."

Sherlock rose up on the balls of his feet, turning in a graceful pirouette that spoke of dance training somewhere in his background. He didn't open his eyes until he'd settled back on his heels, and John saw his whole body expand and contract with a deep breath as his electric blue eyes settled on John.

John was used to watching Sherlock study something of interest as an observer, able to maintain emotional distance between himself and Sherlock as Sherlock took something apart with his eyes and worked out how all the pieces fit together. He'd never been the subject of that interest, and he hadn't realized how powerfully arousing it would be to have Sherlock's undivided attention. Sherlock's hands came together again, the fingertips pressing against his mouth as he walked closer to John.

Looking back later, the whole walk-around probably took Sherlock no more than three minutes. To John, standing in the middle of Sherlock's slow circles, it felt like an eternity. Sherlock didn't touch, didn't get within easy reaching distance. And yet, John couldn't stop trembling under the intensity of Sherlock's regard as his flatmate touched every inch of him with his eyes. John had the sense Sherlock was memorizing, cataloguing, forming hypothesis and theorizing.

At last, Sherlock stopped behind John and stepped closer, his jacket lapels brushing John's shoulder blades as he whispered, "May I?"

John wasn't sure what Sherlock was asking permission for, but he nodded anyway on the theory that Sherlock's wild-brained plans usually had interesting results. He felt Sherlock's smile against his ear, and then the detective was right there, wrapping his arms around John's waist from behind, pressing his fully-clothed body against John's nakedness. John's knees went weak, leaning him against Sherlock for a brief moment before he was able to recover himself. He'd managed to keep his body under control until that moment; feeling Sherlock clothed against him, powerful as John was vulnerable, killed the last of his control.

"Interesting," Sherlock murmured as John's breathing sped up, his heart rate going through the roof as his cock began swelling in arousal. "You seem particularly responsive to this form of stimulation."

"Maybe just a little," John said, doing his best to keep his voice level.

Sherlock stepped away and moved back in front of John, staring into John's eyes. How fascinating that their eyes could be grouped into the same color group, and yet be completely different. John thought of his own eyes as being like still water, with more danger than usually showed on the surface. Sherlock's changeable shades of blue, though, were amazing. They ranged from the hottest part of a flame to the sharp electricity of a lightning bolt. "You are very well put together," Sherlock said, his eyes flicking away from John's. John had the startling sense that Sherlock was suddenly afraid to look too closely. What was he afraid he'd see?

"Thank you," John said. "You'll wear the costume, right?"

"I did promise," Sherlock pointed out, sounding a little miffed that John had brought the subject up.

"Yes, because you've never 'forgotten' to keep a promise," John said, rolling his eyes at his flatmate.

"Not when it's a promise made to you."

John settled back on his heels, surprised by that comment. He was aware that Sherlock regarded most rules of society as mere guidelines, especially the one about keeping promises made. He'd watched Sherlock break promise after promise. But never one he'd made to John. "Oh," he said.

Sherlock looked at the kitchen clock, leaning a little to see around the corner. His curls brushed John's shoulder, making him shiver. "We're going to be late if we don't leave soon," the detective said.

"I'll go get dressed." John hesitated a moment before slipping his hand into Sherlock's hair, tugging the detective's face level with his so he could kiss him thoroughly. Sherlock's body stiffened briefly, then the detective relaxed enough to rest a hand on John's shoulder. The heel of his hand rested on the scar, sending pleasant waves of warmth through John as he deepened the kiss. This was the first time John had taken the initiative and kissed Sherlock first, which made for an interesting role reversal when he was naked. Then John pulled away with a small kiss left on Sherlock's lips as a promise. "I'll be back down in fifteen minutes. Will you be ready by then?"

Sherlock sneered a little at the costume again. "Even the cape?" he asked.

"Mm-hm."

"Fine."

Twenty minutes later, after John had spent his time grinning at Sherlock's sullen expression and how well the costume worked on the lanky detective, the two of them were in the cab to Lestrade's house.

"I don't understand the bubble pipe," Sherlock said, examining it. "If I have to carry a pipe, can't it be a real one?"

"The bubbles are funnier."

"You're lucky I have a nicotine patch. It might not be enough."

"Sweet, remember. You promised."

Sherlock slumped in his seat, but he reached over and caught John's hand in his. "I did," he said.

And he kept that promise, turning the charm up and putting a sheath on his wit as he interacted with everyone at the party. He was even civil to Anderson and Donovan, which was almost enough to get him nominated for sainthood, as they were being particularly nasty. John found himself watching his flatmate rather more than normal that night, remembering the feel of that solid body pressed against his from behind and wondering who was going to take the next step. If there was going to be next step.