Edit: Thank you all so very much for the wonderful response! I wrote this on a whim and your lovely comments and kudos have brought me much joy!
Background: Sherlock and John don't have a romantic relationship...yet. Everything they wrote was taken out of context.
There is now a Korean translation by the wonderful M'e
If I could read Korean I'm sure I'd tell you that M'e did a wonderful job!
"John, can I borrow your phone?" Sherlock could hear Lestrade reaching towards John, the fabric of his jacket stretching. Lestrade was facing John though John didn't even look back before handing his mobile over. Sherlock knew that Lestrade's phone was a very old model and quite rubbish so this was nothing new.
It hadn't taken long for Sherlock to deduce where the woman was from, where she worked, where her husband worked, and who her killers were. He deduced that she used to be a hand model, had an allergy to strawberries, once got her belly button pierced in France, and collected tea cups. Only some of which was useful.
Less than an hour later and Lestrade had everything ready. He had men on their way to collect the killers, all evidence was bagged, and even the victim was on her way to the morgue. Sherlock was ready to whisk John off to a restaurant to celebrate. Then he heard Lestrade’s pocket buzz.
Lestrade pulled out the phone, just then remembering he had taken it from John. The screen showed two missed messages. The latest was from some bloke, probably one of John's old uni buddies. The earlier was from Sherlock. Lestrade couldn't help himself.
"Oi, Sergent Donovan" He called to Sally. Sherlock could see the twinkle in his eye and knew he was feeling mischievous. It was the same look he got when they did a drugs bust. Sherlock was quite familiar with it.
He showed her the series of messages before handing her the phone. She couldn't help but giggle, but continued to scroll through the many lines of chat.
"Ooo 'I need you. SH ' " Sally read Sherlock’s message.
"'Can't. Am at work. JW '" Lestrade tried his best impression of John.
“ ‘Come directly home. Can get milk later. SH. ’ That’s so sweet!” Sally laughed. "Poor Sherlock! Did you have to wait long?" Sally said, making her best puppy eyes at them. She knew full well that Sherlock had been working on this case, but she still liked to see Sherlock squirm a bit. Relationships were never his territory and it was one of the only subjects where she had the upper hand.
Sherlock failed to see how any of this was funny, but clearly everyone else thought that there was something to their messages, so he listened intently to the inflections of their voices on his and John’s words, and observed the glances the coppers were exchanging. Very interesting. Obviously there was something going on here.
"How about this one? 'Buy Milk. Also new bed sheets. SH.' Please tell me that was some kind of experiment gone wrong?" Sally said, pretending to be ill.
It had been, but Sherlock wasn't going to play games. He and John had nothing to hide, naturally, so he resigned himself to giving the two officers his angriest not-bothered face he could muster. What did bother him was that John looked mortified. This was new. There was clearly something to these messages.
"'Am hungry. SH.'"
"'Am working. Made reservations. Angelo's, 8. JW.' A date then? How romantic!"
The giggling continued before Sally's thumb paused on the screen. She smiled sweetly--genuinely--before giving Sherlock a look that can only be described as "Awwww."
Lestrade noticed the change and read over her shoulder. He looked up at John and then Sherlock, repeating Sally's expression.
Sally began: "'Answer my texts! It's been 3 hours. SH' Sherlock, what'd you do to John?"
Lestrade continued: "Am fine. At pub. JW."
"'Sorry. SH' I didn't think that was possible," Sally continued.
"Not upset. With friends. Will be home soon. JW "
"Or this one!" Sally took a breath to begin. Sherlock noticed John tense suddenly. Obviously John knew what their game was and wasn’t happy about it. Maybe Sherlock should have been mad too. He still wanted to figure out what was so abnormally funny about his texts. “ Do you need me? JW .”
“ Of course. Always. SH ” Lestrade read, with a flowing emphasis on the second bit.
“ Cancelled plans then. Will meet you there. JW ’ That is just so sweet. You two!” Sally cried, smiling brightly at Sherlock. He narrowed his gaze on her.
He had calculated by now that this was something to do with the relationship between him and John. By the mention of the sheets, the restaurant, and now some sort of “you two” like they were a couple Sherlock was beginning to pick up on their game. He wasn’t thrilled. Although, noticing it now, John appeared even more embarrassed than before.
“Yeah, yeah. Alright guys. Fun’s over” John said, walking towards Sally and reaching for his phone.
“Oh no. Not yet. There’s one here I just have to read.”
At that, Sherlock noticed, John grew frantic. He grabbed Sally’s arm and tried to take the phone with his other. Lestrade intercepted.
" Don’t go without me. JW " Lestrade read, pretending to be John again, turning his back to the doctor. John gave up fighting and turned to pleading.
“Please Lestrade, don’t” John said quietly, hanging his head.
“ You’d better not have gone. JW. ” Lestrade continued. “ Oh, God Sherlock. Please respond. Will text Mycroft. JW. ”
Lestrade started to say something next but stopped. He looked at John and his eyes softened. Sally, not picking up on the exchange, took the phone back and read it instead: “ I love you. Please be alright. JW. ” Sally clapped her hands with joy. “Oh John! That’s so swe—Oh…Oh my God…I’m” she looked back down at the phone and quickly handed it over to John. “I didn’t notice. You never sent…I’m so…God, John.” Sally looked around uncomfortably.
Sherlock could see that John felt helpless. He hated seeing John like this.
Lestrade broke the silence, “Sorry mate. Got a little carried away.” Lestrade tried for an awkward laugh, staring at John the entire time, “You guys are good friends, eh? Best mates. Well, good for the both of you. I—“
He was cut off by the buzz of John’s mobile, still sitting gingerly in John’s hand.
John looked down at it to find a new message. It was a text.
“I love you too. SH. ”