Sherlock Holmes never really meant to fall in love, not with anyone, and certainly not with John Watson of all people. But it turns out that denying your entire body what it so desperately needs is close to impossible. The first time Sherlock kissed John, he felt like the entire world had stopped moving. That it had even stopped orbiting the sun. The raw emotion he felt almost choked him. Too many feelings, too many thoughts and sensations setting his skin alight, igniting some blaze in the pit off his stomach. His heart suddenly felt too big to be contained in his chest, like his ribs were about to shatter and perforate his lungs from the pressure of it.
And then John's tongue slid against his own and his brain sparked and shorted out. The vague taste of peppermint toothpaste masked by the tea John had just drank and oh yes that was very, very good. Warm and wet with just the right amount of pressure. Before he knew it, Sherlock was whimpering and moaning into John's mouth, and he was sure that everyone in Baker Street must be able to hear his erratic heart it was beating so loudly. But John didn't seem to mind. Their kisses became more urgent, demanding, yearning. They made love and it was awkward and clumsy and messy and yet so perfect. Sherlock was sure he was about to die as his vision went white and his whole body shook, because surely nothing, nothing could feel this good?
And oh, but it could, because Sherlock was decidedly not dead. In fact, he was very much alive. And for once, his mind was quiet. No thoughts barrelling around and bouncing off each other, striking the inside of his head and hurting, just hurting with all the information they contained. No burning desire to tear his hair out of smack his head against a wall just so the thoughts would stop. Peace and quiet and John, warm and comforting resting beside him. Gentle fingers tracing idle patterns on his chest. Muscles loose and relaxed, all tension long forgotten. Murmured words of love and adoration hanging in the air, heavy with meaning, almost suffocating with their truths.
Sherlock said them back. Not because he felt like he should, or because his brain was so addled he couldn't process his thoughts properly, but because he meant them too. And it's true that his thoughts were addled, but only the ones that were unimportant, irrelevant. Because what mattered then, in that moment was that Sherlock had fallen in love, and there was no way out of it now.
After that, things were difficult for a while. There were family disagreements, lots of anger and hot tears. Stares in the street and homophobia and insults. The world is a dark place, full of evil and hate. People who believe that they're right but couldn't have been more wrong. But Sherlock and John made it through. Because that's what they were: Sherlock and John. Always together. Work partners, flatmates, friends, lovers. Words that described them but could never really define them. They were undefinable. Bound by their need for each other, tied together by some invisible thread.
Now, they wish that they could live in each other's skin. Sherlock wants so desperately to crawl under John's skin and stay there, safe and warm and needed. Because that's what John is to him. He's not just endless cups of tea and plates of unwanted food, given in good faith. He is warmth and safety and everything. And John has inexplicably entered into every part of Sherlock's life so that now Sherlock feels like he can't breathe without him there. John is under his skin, pushing into his veins and into his blood, and forcing his heart to beat, and to keep beating for him, for John.
They stay that way; a part of each them inside of the other. Underneath their skin. Safe. Warm. Loved.