"Y-You're a vampire?!" John exclaimed, and Sherlock sighed. He honestly expected a slightly more intelligent response to his confession, but had forgotten once again that John was just an ordinary person. However, even if he were ordinary, he still trusted John with his biggest secret. Bigger than his drug habit, bigger than Red Beard. Sherlock Holmes was a vampire.
"Yes, I am. Isn't it obvious?" Sherlock rolled his eyes and watched as John's eyes over his flat mate, whose fangs were now protruding from his mouth, along with beautifully deep crimson eyes, the exact opposite of his pale skin. John gulped and moved back slightly. "Why wait until now to tell me, Sherlock? You could have told me this so much earlier on! I would have been able to help you, get blood bags for you! I am a doctor, I do have access to blood" At the sheer mention of the word blood, Sherlock's eyes seem to widen considerably, making John feel incredibly nervous. He knew the myths of vampires, of course he did, everyone did, but he was just hoping that Sherlock wouldn't even dare
Sherlock sighed. "I had suppressant tablets I could take so that I appeared to be physically human, although I would still be immortal, I just wouldn't crave blood, or have fangs, or red eyes" John nodded. "But I can see your fangs and eyes" He moved back. "So I presume you're craving blood too" Sherlock nodded and John's pulse skipped a beat. "Mycroft stupidly mistook my suppressants for drugs, and so has cut off my supply of them, leaving me vampiric once more" John's breathing rate quickened, along with his heartbeat and Sherlock's head snapped back up to look into John's eyes. "I'd advise staying calm John. I can smell your blood" Sherlock sniffed deeply. "It's so rich and warm and hot and I want it so much!" John bolted to his feet and so did Sherlock. "A Positive, am I right" John nodded and kept looking at Sherlock. "You need to calm down, Sherlock. You're getting carried away. I can go down to Bart's and get you a blood bag, but you are not drinking from me!" John clearly stated and Sherlock slowly nodded. John didn't let his guard down, his military training helping him to prepare slightly. They would never prepare soldiers for vampires...
Sherlock emitted a low growl and took a step towards John, making John take a step back. "No! I refuse to drink that processed rubbish" Sherlock smirked darkly. "I prefer blood freshly drawn from the victim using my own fangs. Still warm from their pathetic, easily broken bodies" John moved his hand towards his gun, hoping that would help deter him as he drew it. Sherlock laughed at the sight of the gun and moved to John at lightening quick speed, smacking the gun out of his hands. "Idiot. You only have to look as far as movies to know they won't work" Sherlock sniffed the air again. "I love scaring my victims. It fills the air with the smell of their adrenaline and fear. It's a truly fantastic smell" He pushed John into the wall, pinning him there by his shoulders as John gasped breathlessly when all the air was pushed out of his lungs. John stated up at the tall, dark man. This was the end.
Sherlock leant in and sniffed his neck, moaning for the smell. "It's been long. Much too long" Sherlock stuck his tongue out and licked at John's neck. "I can even taste your fear" John did his best not to react to Sherlock, but couldn't help cringing at his lick. "S-Sherlock!" Sherlock out a finger to John's lips. "Hush now. Don't yell out, it'll only make this worse" Sherlock leant in and bared his fangs as he bit into John's neck.
John groaned, half in pain from the bite, half in pleasure from the chemicals Sherlock was releasing into John's bloodstream to stop him from fighting back. He felt Sherlock's fangs in his neck and heard the repulsive noises he made as Sherlock sucked in his neck and drank the blood up incredibly quickly. Soon he'd drank so much John couldn't stand, and went weak in Sherlock's arm, but he was just held in place by Sherlock who was still drinking him. He shakily put a hand out to try and pull him back, but Sherlock's fangs were latched into his neck. "P-please stop" John hoarsely groaned out, but Sherlock didn't listen and kept lapping up John's blood.
He eventually pulled away before John collapsed and died completely, swooping him up in his arms and taking him to his room. He lay him down on the bed and smirked again, stroking his neck where the bite marks where. "My little blood bag" He put the quilt over John and pecked his forehead, before turning the light off and locking John in his room, ready for Sherlock to feed on later if he desired to, which of course he would do. John gained enough consciousness to get to the door and tried the handle, finding it locked and screaming internally. He was doomed to spend the rest of his life as Sherlock's blood bag.