The first time Sherlock's mother looked at her and commented on her growing breasts, saying that they'd have to get her some bras soon, Sherlock spent the rest of breakfast picking at her food before grabbing her bag and leaving for school. She didn't say anything.
That afternoon, she looked up how to prevent breast growth. She found a page about the physiology of a breast. The website said breasts were mainly fat, with some lactic tissue thrown in. It couldn't be too hard to prevent, right? She started eating less, showing up for fewer meals and nibbling at her portions when she did show up.
When she passed out while she got dressed a week later and Mycroft found her and asked her why she had stopped eating, she shook her head. She couldn't explain why the idea of having breasts made her stomach roil.
He made her come to meals again, and watched her plate to be sure she ate. Sherlock counted every calorie, watching with dismay as her chest swelled and drooped into breasts over the following weeks and months.
Her mother bought her bras, and Sherlock made sure to choose the ones that gave her the flattest chest, sports bras holding her breasts in and up, smaller, while she looked for something to do the job better.
When she turned fourteen, she entered the school's boxing team. She was a lightweight, wiry and slim, but flexible enough and strong enough to win, with some training. She went to championship the year she was seventeen, and learned to wrap her knuckles to prevent smashing the bones of her hands.
Protecting her knuckles didn't protect the rest of her body, however, and all it took was one kick to crack three of her lower ribs. She lost the fight, and was taken to the paramedic waiting on the far side of the gym. He taped her ribs to restrict movement, and gave her a roll of bandages to exchange for the tape when she needed to shower.
That night, as she wrapped the bandage around her ribs, she paused, looked at the way the bandages compressed her skin, made her torso narrower, slimmer. And then she wrapped upwards, layering over her bra and down again, until her whole ribcage was wrapped in compression bandages. Each breath hurt, but even so, when she pulled on a shirt and looked for the first time at her flattened chest, she breathed easier.
Once her ribs healed, she was able to wrap her breasts tighter, tugging the sagging bandages closer each day. Her chest hurt constantly, and bruises formed across her chest, spreading under the skin. It didn't take a genius to know what the creaking of her ribs meant.
No one was any the wiser until, when she went for her annual checkup, the doctor felt her ribs and she gasped in pain, unable to hide her discomfort. He left the room to speak to her mother, and when he returned, a more thorough examination took place. The bandages were discarded while she looked on helplessly.
It was like deja vu to have her ribs taped in place, but this time, because it was summer vacation, it was Mycroft who replaced the tape each night, helping her tug her discarded sports bras on in the morning. He never met her eyes while he handled her body. Her mother kept asking her who had hurt her, who had broken her ribs, why she hadn't told them about it instead of trying to bandage them herself. Sherlock didn't respond, simply looked away.
It is Mycroft, when his ribs are healed, who takes him aside and presents him with his first compression shirt. It ends at his hips, presses his breasts down flat, and while it's still hard to breathe, he finds that he can move better and breathe easier than he ever could with bandages.
Mycroft watches him smooth his hands down his chest, admiring the way the binder is almost invisible under his shirt. It is he who puts into words something Sherlock has been scared to admit, even to himself, for almost five years now.
"It suits you well, brother."
A/N: This story deals with gender issues and non-graphic broken ribs, as well as ACE bandages used to chest bind. ACE bandages are unsafe to use for chest binding, as they are designed to tighten with movement instead of moving with your body- namely, your ribcage when it expands to accommodate breathing.
Please, please, please do not bind like this. It's dangerous, and can actually break your ribs, as well as cause skin irritation and, in some cases, suffocation. Please use a proper binder if you feel the need to bind. They can be found and purchased at such sites as Underworks, Les Loveboat, eBay, and Amazon. The ones from Les Loveboat can be bought for a little more than ten dollars, if you're looking for something cheap. They are designed to move with your body while compressing your chest safely, though still should not be used for more than eight to twelve hours at a time.