Disclaimer: Sherlock belongs to BBC, etc, and of course the original characters were Conan Doyle's. I'm just having fun with this.
This has been bouncing around in my head for a while since I ran across a few of the soul-mate fics. I have no idea what the original prompt for those was, but here's what I've ended up with. I think there may be a few related short stories after this one, but I'm posting it as a one-shot right now, and we'll see what happens after.
John stared at his left arm that morning for a long time before he finished getting ready for the day. It was another day with nothing to look forward to. He didn't even have an appointment with his therapist. His blog was nearly blank. Nothing happened to him now, and certainly no one would want to bother with him. He sighed, reached for a patch from the box on his nightstand, and slapped it over the mark on his arm before putting on his shirt and jumper.
Everyone wanted to find their soul-mate. Most did. It was easy enough to verify. Everyone had a mark on their right or left arm, half of a circle that swirled in a unique pattern. Your soul-mate had a mirror image of the half circle on the opposite arm. You were born with it. It was such a unique part of the self that in the absence of fingerprints or dental records, a body could be identified using their mandala.
There were endless websites devoted to finding one's match—sign onto a forum, go to your colour, and pick left or right and start searching. It was incredible how often people just bumped into each other, though. You could also make a request through the government ID agencies (for a fee, of course), but your soul-mate had to have ticked the box that allowed the release of information. And, of course, if they were underage, even if they had a passport, you weren't permitted that information until they reached eighteen. Needless to say, going through the government was not the most popular option.
The strict cultural rules surrounding mandala matches had relaxed over the last century, but traces still remained. It was considered rude to simply stare at another person's mandala, and most people kept around a box of the large skin-toned plasters to cover theirs with. For doctors, this was as much a part of the uniform as the rubber gloves. Asking someone's colour was the quickest way to discover if they might be your match. If your colours matched, then you moved to comparing mandalas. When you found your match, the two of you began wearing copper rings on the respective hands to signify that you were no longer searching, moving up to silver when you became engaged, and gold once you married.
John Watson had yet to meet anyone with his colour. He was a silver, one of the rarer shades, and while a left-handed silver should theoretically be easily able to find a right-handed silver, the truth was that the rarer your colour, the harder your search became. The sections for the rare colours on the online forums were short. It was easy to realize that his match was not there. He eventually took his profile down, since it never seemed to attract anyone. Once he was posted to Afghanistan, he gave up searching. It didn't really fit with the life he had chosen. If he stumbled across his soul-mate, well and good, but if he didn't, then he would live his life alone.
He started to wonder whether that had been a smart idea when he woke up in the hospital after being shot.
When John returned to England, he was almost entirely alone. His sister and her soul-mate were separated and possibly getting divorced due to Harry's alcoholism, and neither was in a place to put up with him. Most of his friends had either been in the army, or had moved out of London. His therapist did her best to convince him that he needed to do something with himself, but nothing seemed to click until a chance meeting with Mike Stamford introduced him to Sherlock Holmes.
Sherlock was another person who had yet to find his soul-mate. As far as John could tell, Sherlock might not even be actively searching. He certainly didn't seem much interested in that sort of relationship. He kept his mandala covered with either long sleeves or a patch and never brought the issue up. He told John something about being "married to his work."
That was fine with John. Sherlock was vibrant enough without a soul-mate to complicate matters. He wondered who on earth would be a match for the man, and assumed that they must be as extraordinary as Sherlock.
John started blogging their adventures, and after a couple months, decided it was time to start searching again. He was functioning better, and he had something more to offer a person than a broken-down ex-Army doctor with a bad leg and a case of PTSD. So he went on dates.
After the first one, he came home and collapsed into his chair. Sherlock glanced up from an experiment. "Wrong colour?" he asked.
"Orange," said John. "Orange. And really weirdly obsessed with fashion."
Sherlock snorted. "Waste of time, John."
It became a pattern with them. John would come home after a failed date, make a cup of tea, and groan. Sherlock would idly inquire about the colour and John would complain about it. Sherlock never bothered to ask John's colour, but at one point, he did ask John why he bothered only dating women.
"I've tried dating men," said John. "No luck there, either. And they seem more inclined to ask for a bit more than just dinner."
"Ah," said Sherlock. "So you subscribe to the societal attitude whereby one postpones sexual intercourse until meeting one's soul-mate."
"Sort of," said John. "I get that not everyone wants to do that, and that my soul-mate might not have done that, and it's okay, but I just...it doesn't feel quite right to me. Why, are you in favour of it?"
"I have no basis for comparison," said Sherlock. "I have never met anyone with whom I wished to attempt becoming that intimate, soul-mate or not. Sex involves more complicated emotions than I currently wish to engage with. Emotional entanglements would be a nuisance. I understand both principles, and while postponement certainly offers a great deal of advantage when it comes to preventing STDs and unwanted pregnancy, most people these days appear to regard those as less hazardous than not knowing how to perform."
John snorted. "Right, because it's going to be the same with every partner. From what I've heard, it's different with everyone, so you're still stuck figuring out what works and what doesn't. I've never wanted the extra emotional tangles that come with sleeping with someone who's not your soul-mate, and the STDs and pregnancy were sort of a secondary thing. And what if I was involved with someone physically and then ran into my soul-mate? How would that go over?"
Sherlock rolled his eyes. "People are far too emotional about these things."
"Yeah, well, sometimes emotions are good, Sherlock."
Several months later, Sherlock lost patience with John. He came in from a date and said, "Pink," in a tone of deep distaste. (There was an entire branch of social science devoted to determining whether one's mandala colour affected one's personality type, and in general, pinks were supposed to be airheads).
"What colour are you?" Sherlock demanded. "You come in, week after week, date after date, and none of the common colours match. Red, green, pink, indigo, lavender, none of it."
"I'm silver," said John, blinking. "Have you been trying to deduce my colour?"
"Well, yes, of course," said Sherlock. "It's not like you walk around with your mandala uncovered like some idiots, but I have run out of patience and—silver?"
"Yes, silver," said John. "I'm a rare. I've never even met another silver."
"Yes, you have," said Sherlock in a odd voice.
John stared at Sherlock. "You're a silver," he said flatly.
"I've never met another either," said Sherlock. "Not until you." He stared at John, who couldn't quite read the expression on his friend's face.
"Okay," John began, "if this isn't—if we don't—well, it won't make a difference, okay?"
Sherlock nodded and rolled up his right sleeve. John did the same with his left and they held out their arms.
"I told you all those dates were a waste of time," said Sherlock after a pause.