"John…"
John turned around to the shuffling form of his friend, raising an eyebrow. "Yes, Sherlock?"
The doctor waited for the genius to speak patiently. Whatever this was, Sherlock seemed mildly uncomfortable about it. Sherlock took a breath and shoved a black box into his flatmate's hand, words coming out in a quick blur, "Will you marry me?"
John stared at the ring box and back up to Sherlock's face, jaw slack. Finally, he found his voice. "Well, Sherlock. What brought this on? I thought you were married to your work?"
"That's the thing, John," Sherlock began explaining, his previous discomfort fading, "you are a part of the work. You run through London chasing criminals with me, listen to my deductions," (look sexy while killing bad guys) "and you're just there, on every case. By the Transitive rule, if I am married to my work, then I would be married to you. I thought we should make it official."
Sherlock looked expectantly and John laughed a little, "You know what, I might as well. We fight like a married couple already and I'll never hold a girlfriend with you around. Let's get married."
Sherlock smiled, "May I kiss you then?"
(Mycroft then attempted to tear the two apart for Sherlock's wellbeing. What he got in return was a hearty Fuck you)