The first time they kiss, it is by accident.
There is no drawn out speech. There is no dancing. There is no candle-lit dinner or slow, romantic music. Instead, there is the peal of ambulances and fire engines, broken bones and blood and flashing blue lights that illuminate their faces in the half-light of the clouded moon. There is wind whipping at Sherlock's hair, fingers skittering over eachother's faces, damp hair plastered to their foreheads, looks that say nothing to those watching but to both of them means you're alive and a rush of heady laughter that bubbles up from their chests, falling from lips flecked with dust from the explosion.
The first time they kiss, it is no more than John tilting his head upwards at the same instant Sherlock tips his down; it's no more than a barely-there brush of lips. It's really more of the two men exchanging breath, the swirls of it dancing, mixing together in the harsh chill of the night as they stand beside each other, as they have done since the moment they met, wrapped in thick orange blankets and thanking Gods that neither of them believe in for saving their lives.
"Nunc primum," Sherlock whispers to himself, letting the wind carry his words away into the star-spangled sky.
After that, they become less tentative. They let their hands brush when they walk, John's fingertips grazing over Sherlock's knuckles in a delicate caress, their ankles interlocking under the table when John convinces his flatmate to eat something, damn you, you're getting too thin!
Their kisses progress to more. The once hurried and precious butterfly kisses they pressed to foreheads and cheeks become an intricate array of blazing, tumultuous hurricanes of teeth and tongues and blood and more; their once shy hands and mouths now feel out the planes of each other's torso, committing their bodies to memory in a whisper of taste and the press of fingertips. It is as if their first kiss touched raw nerves, setting off sparks of life in the other.
They love every aspect of what they have become - what each of them is. Sherlock, the ever ingenious man, loves John. He loves even the slight flabbiness that John is accquiring (a present from the amount of chinese take-away the two consume), the soft dishwater coloured hair that is beginning to receed with age, the lines and creases and scars of his war-torn body, the soft sticky flesh of the middle-aged man he has become.
John, the loyal doctor, adores Sherlock. Where others hate him for his sharp tongued comments, uncanny deduction skills and sociopathic tendancies, John can find nothing he loves more.
He likes to think to himself, in the privacy of his bedroom with Sherlock curled against his chest in a deep sleep, that they make up for each other's faults; that they are pieces of a jigsaw, the holes in their edges joining perfectly to fill in the other's missing parts, making up a larger picture, painting themselves in obscure patterns across the walls of their apartment in bright colours. Like most masterpieces, John thinks as he watches the rise and fall of Sherlock's chest, It's something that nobody will understand until we're dead. And he isn't wrong.