Bit of Sherlock being a naughty pervert here. Relatively explicit, read at your own risk.
The soft, muffled, tell-tale grunts are emanating from the shower again. Quietly, Sherlock stands at the door between his bedroom and the bathroom. John's form, so solid and recognisable, is obfuscated by the pebbled glass and the shower curtain, but the noises and the repetitive motions make it clear what he's doing.
Sherlock bites his lip, studying the shifting musculature of John's back through the haze. One hand drifts down, idly palming the stirrings in his trousers. Somewhere in the back of his mind, he knows this is wrong, but it's so fascinating. How is it that John, doing something so mundane, so inelegant, so base and so utterly human, is so interesting - not to mention arousing - to Sherlock? Why is literally everything about John so captivating?
A quiet sigh escapes his lips, his hand grinding harder and faster against the front of his trousers. John's picked up the pace; if he's following his usual pattern, he's nearing orgasm. Sherlock undoes his zip, slides his hand into the front of his trousers and cups his erection, his shoulders mimicking the movements John's making in the shower.
With one loud groan, Sherlock climaxes, warm come flooding his pants, his trousers still hanging from his hips. He leans heavily against the wall, trying to catch his breath as his knees buckle.
