Shep has never had any illusions about their own psyche. Analysis is one of their hobbies, after all, and a poor analyst they would be if they did not know themself. So when they grew older, they handled puberty with all the deftness they demonstrated in their writing. And, unsurprisingly, they handled the attractions of certain sexual practices with ease. they believed it's because of their exposure to the internet's more filthy corners at a young age. Dev thinks it's just how he is. But then, Dev tends to see only the surface of things.
Dev and Shep get together after a drunken night of celebration. It had been Storm's seventeenth birthday, and they had all consumed a little too much alcohol. Shep's mother took them and Dev home, as they were able to drive even while intoxicated whereas Dev's father would not be pleased with being woken at three in the morning. So they collapsed together onto Shep's bed, the door closed firmly and their clothes in disarray, and lay there waiting to sober up a little. By the time the alcohol had started to wear off, they both came to the realisation that it was really very hot and they should take off their clothes shouldn't they?
One thing led to another, and they became a thing. Not a couple, exactly. Nor was it a friends-with-benefits arrangement. Neither knew quite what to call their relationship for several months, until Shep did a bit of online shopping and began to formulate a proposal.
The proposal involved, quite simply, a set of soft ropes and a blindfold.
Dev took the proposal well. He wasn't naive by this point; far from it. He had delved into porn, from the mundane to the extreme, and he was interested enough in it to consent after a fairly long discussion. They both chose safewords.
Shep chose "Cthulu", as their pronunciation of the word was well practiced and they highly doubted they'd say it during sex under any circumstance otherwise.
Dev chose "Ectoplasm", as his fascination with ghosts had persisted long into his teenage years and remained strong today.
- two years later -
Shep ensured the ties weren't cutting off circulation, their small hands quick and skilled on the soft rope. Dev lay on the bed, naked but for a single piece of blue cloth covering his eyes, and sighed. Shep paused.
"Alright, pet?" they asked, their voice deeper than it had once been but still unquestionably feminine.
Dev nodded, smiling, "Yes, I'm fine Master." While he was with them, in a session, he would call them master and they would call him pet. It was how they worked. Outside of a session, they were best friends - they weren't in love, per se. They just needed each other on a level not many could understand. Dev was devoted to them, and Shep was protective of him, but they would never call each other pet names or get married. They were pet and Master, and that was alright by them.
Shep smiled down at him, before getting off the bed and stripping down. This was one of their favourite parts; to touch him, tease him, show him tenderness and pain simultaneously and at the same time not allow him to return the favour. they loved his face when they touched him, the gentle arch of his back, the bite of his teeth on his lip. they liked the high keening noises he made, and the fact that he wouldn't beg them until they  gave him permission to speak.
they slid their fingers along the inside of his thighs, parting his legs gently. They kissed along the lines their fingers had left, listening to his breath shudder out. they mouthed at his balls, before rolling them with their fingers. Shep licked a line along his shaft, flicking their tongue just so when they reached the head, before kissing his hipbones. they moved up his body, their knees indenting the bed on either side of his hips, their breasts pressing up against him. they kissed him, slow and deep, scratching lines down his torso.
When they took him into them, he moaned just like the first time.