With a man like Sherlock Holmes, everyone would've assumed that the girl he fell for would be nothing but an intellectual that made his gears tick endlessly every moment they were together. How else would a high-functioning sociopath survive?
Sherlock himself never thought that his brain could ever stop thinking, never stop turning cases and information and bits of knowledge over and over and over, just analyzing everything he deemed important enough.
But the girl he fell for, oh, the sweet girl with soft eyes and a sad smile who made his world go mute. He couldn't focus on anything but the way the sunlight hit her through the windows as she read her books on his favourite chair. Where his attention should have been separated simultaneously amongst at least five different cases, as it always was, his genius working a mile a minute. His subconscious always thinking about what was the next move or his theory was corrector what to make of Mary and - always, always thinking.
It was silent; focused on a single person.
Hair of gold and a glint in her eyes he could never quite make out despite all the genius he so enjoyed showing off. The girl was transparent as glass and yet he could never make out those damned eyes. She was a paradox taken form he couldn't solve, and he loved it.
It wasn't love at first sight where his world instantly just stopped and he saw nothing else but her as if she were a neon sign in the dark. Sherlock says it was a slow fuse that had burnt without any sparks or sound. One afternoon while he droned on about the "Invisible Killer", he happened to glance at her sitting under the sun solving the daily crossword on a newspaper Mrs Hudson had so kindly gotten for them the day before. And he realized that he'd stopped talking and the gears that ran his brain had stopped moving. For the first time in Sherlock's lifetime, his mind was silent; not a hint of the onslaught of information and theories that usually filled him.
Just... muted.
And then he was speechless and terrified that he'd somehow managed to lose his brain.
He passed it of as nothing more than a once-in-a-lifetime moment, all but choosing to it. But then it kept happening more and more frequently, always realizing that he was coincidently staring at her when he snapped back into the constant chatter of his own mind. Until he remembered there was no such thing as a coincidence.
And that's when he knew he was in love with the girl who chose cola over tea, who dressed like a lazy sunday afternoon rather than a busy friday night. Who always smiled at him no matter what kind of trouble he'd caused, who always took the chance to run her fingers through his curly hair whenever it was in her reach, despite his half-hearted protests. The girl who smelled like cocoa butter and took each breath like the world wasn't a self-serving wasteland.
She, who let him sleep peacefully without needing to use his sleeping pills he'd so perfectly managed to keep a secret and allowed him remember how nice it felt to be touched just for the utter sake of it, who reminded him that not everyone had ulterior motives and that kindness did exist, no matter how scarce.
John thought they were such an inconceivable pairing; a girl who lived in the sun and a man who worked in the shadows. He was stunned when he came to visit with Mary one day and found them fast asleep on the couch together, her one arm hugging him close and the other entangled in his hair. Suddenly the loft seemed like a different place to John, without Sherlock prancing around and spouting whatever came to mind in his merriment of exciting cases. It was... peaceful.
It occurred to him how specially rare it was to catch Sherlock sleeping in the first place, the man normally refused to, being too paranoid or occupied with all his enemies and cases. He only slept when he absolutely had to. For him to let his guard down in the middle of the day in plain sight was... John couldn't believe it.
The girl then lazily opened a single eye and quietly motioned for them to leave, stirring John out of his stupor and mouthing a silent apology before going back to her land of dreams. She understood perfectly well how dangerous their enemies were, she simply chose to not be afraid. And then John understood why Sherlock had fallen for her. It was because she didn't try to avoid the shadows, or was oblivious to its existence, it was because she stared it straight in the eyes and cut right through it, leaving in her footsteps what could only be her very existence, wherever she so dared tread.