A/N: The extra naughty scene that everyone wanted! I'm not really setting it anywhere in the timeline, so you can make it whenever. Personally, I prefer an extra naughty Sherlock and this was before they shared a kiss.
Shameless smut with the mirror aka voyeurism.
He tried not to think of it as spying. If anything, the only reason Sherlock was checking up on John using the mirror was because he was afraid that the other man would try and escape...that was the only reason.
Sherlock's heartbeat did not become faster and he certainly did not get a thrill at saying, "Show me John Watson."
The mirror's surface swirled and Sherlock's reflection was replaced with the sight of John laying on his bed. He looked as if he was asleep and Sherlock's face fell. I'll just watch for a few minutes. It couldn't hurt anything, could it? And besides, as Lord of the castle, Sherlock owned the right to see John whenever he wanted...even if John wasn't aware of it.
John was still for only a moment then his hand began to trace up and down his chest. Sherlock looked on transfixed as John's fingers brushed up and down his chest and farther towards his abdomen. Sherlock's mouth went dry.
John's eyes barely opened. They were heavy and he looked completely relaxed. John's hand finally went down to his crouch and it gently move along the bulge that was beginning to form.
Sherlock couldn't peel his eyes away from the enchanted mirror as he watched the scene unfold. He never would have ever thought he would see John do this. Still that didn't matter because now that he had seen the beginning, Sherlock knew he won't be able to put the mirror down until John either stopped or-
With a deep blush spreading over his cheeks. Sherlock watched transfixed as John started to open his trousers. I shouldn't be watching this. If John ever found out I watched him...Whatever logic his brain tried to throw at him it didn't matter. Too much blood was being redirected to his groin and Sherlock's brain soon stopped trying to offer any resistance.
Sherlock's eyes didn't move from the mirror as he walked slowly to sit onto the nearest chair. His legs weren't going to keep up his weight; they already felt like jelly and John had barely even started.
John's eyes had closed again. His hand flicked the button of his trousers open and he slowly brought his zipper down. Opening his trousers, he brought the heel of his hand down so he could apply more pressure to his half-erection.
Sherlock knew that his own trousers had become unpleasantly tight and was suddenly tempted to open them up. I'll just open them. That's all. I'm uncomfortable. Yes. Sherlock wasn't going to touch himself; he just needed to relieve some of the pressure that was building up.
John wrapped his fingers around his now hard cock. He pulled slowly up and his body arched forward into his touch. Sherlock's eyes grew hazy as he watched John touching himself. It was becoming even more difficult for Sherlock to keep one hand planted on the arm of his chair and the other gripping the mirror.
John's tongue peeked out from his lips and licked slowly along his lower lip. Sherlock found himself copying the motion and wishing that it was his own tongue glossing along John's full lips. Sherlock let out a moan and brought his hand to rest on his thigh.
John scooted up and wiggled his trousers down. His fingers played along the blonde thatch of pubic hair before dipping down under his pants' band. Sherlock's nails dug into his thigh as John brought the band of his pants down to expose the top of his erection.
His thumb rubbed up along the head of his cock and Sherlock could see pre-come glistening on his finger.
Sherlock only blinked when his eyes had begun to burn.
Sherlock didn't even realize that his hand had moved to his crotch until he let out a content sigh. How could he not? Watching John pleasure himself was the most erotic sight Sherlock had ever seen. He had no idea another person could affect him in such a way and the temptation to find release while watching it was too much.
There was no denying that he was attracted to John Watson. One would have to be blind not to see the military strength, the straight sure way that John carried himself. Sherlock just had never thought of John touching himself in such an intimate fashion...or how it would feel if John touched him in the same way.
Sherlock's cheeks burned when the thought popped into his head. I don't have to wait to know what it would feel like to have John touch me. He could mirror John's motions; every pull, every stroke Sherlock could do the same to his cock. Without a second thought, Sherlock brought out the tip of his cock from his pants.
There was already pre-come and Sherlock used it to drag his finger along the top of his erection the same way John had only moments before. The thrill of knowing that what he was doing was completely improper, so not good it had his cock even harder in his hand.
John used both hands to move his pants down until his entire length was exposed. Sherlock promptly forgot to do the same, transfixed at the sight of watching John strip. He had never imagined another person could make him feel so...aroused. His entire body was too warm and every touch was magnified. Sherlock eventually brought his length out and gave it a quick tug, unable to take the ache.
John seemed to feel the same way as he quickly brought his first up and down around his cock. He slowed his movements and his other hand came up to pinch at his nipple through his white shirt; it was bunched up and Sherlock could see all of John's tanned stomach.
Sherlock bit at the inside of lip as his hand moved. His touch was light but the pressure was enough that Sherlock didn't have to worry about orgasming before John. He refused to finish until he had watched John spill himself. Just that thought made Sherlock groan. It was difficult to control all the sensations erupting over his skin and he could come in just a few strokes if he wasn't careful.
John made a fist with his hand and was content to bring his hips up into it. Although everyone was far from his room, John made little noise. Sherlock wondered if it was because John was afraid of being caught by the other residents of the castle. Would he make more noise if he was with someone else?
Sherlock had been able to tell the moment his eyes had got their first proper look at John that he was bisexual. Sherlock had only ever been interested in men, but he couldn't blame John for being interested in both sexes. Sherlock had tried not to think about it too much. Why would John ever want him? But the sight before him was making Sherlock entertain all the desires he had pushed to the back of his mind.
Sherlock brought his thumb up again over the sensitive head of his cock. His hips bucked forward slightly and Sherlock hoped that John wouldn't be able to last much longer. The wait was almost becoming too much. Sherlock's eyes roamed all over John's exposed body trying to memorize every curve.
John brought his legs up and soon his feet where flush on the bed. He thrust his hips up and his movement became heated and erratic. John brought a hand up to his mouth and inserted two fingers into it. He thrust the fingers in and out as his thighs began to tighten.
Sherlock couldn't believe what he was seeing. At the peek of his arousal, John had let all self-restraint go and had properly started to fuck both his hand and mouth. Sherlock let out a growl; annoyed that his other hand was holding up the mirror. Sherlock wished he had moved to the bed as he slipped down the chair, allowing his hips to move easier.
Although John wasn't making much noise, his breathing picked up and Sherlock heard him moan between his fingers. With one final jerk up, John's body stilled as he started to come. Sherlock looked on, transfixed as come splattered against his exposed abdomen and chest.
Biting down a particularly loud moan, Sherlock came. His arse clenched as his body shook with the power of it. His hand was covered in slick come and his pants were ruined. It took another moment for Sherlock to ride through his high and look back at the mirror.
John was already sitting up and pulling off his shirt. He used it to clean up and wiped his fingers on the white material. He put himself back into his trousers and fell back onto the bed.
Sherlock waited until John had fallen asleep to put the mirror down. After that, his eyes glossed over lost in thought. What have I done? The most troubling thought of all was not the lack of guilt but the new awareness that he had been missing something his entire life and he now knew it was John Watson.