Relationships: Sherlock Holmes/John Watson, Irene Adler/Sherlock Holmes
A Scandal in Belgravia Coda

Upon seeing the photos that Mycroft had presented to Sherlock, John hadn't had the faintest clue the kind of impact that one Irene Adler would have on his life. Instead he was blindsided by Sherlock's infatuation, so much worse than with Moriarty, which John hadn't thought anyone could possibly top.

I'm not gay, John had told Irene, not yet understanding why everyone seemed to think he was. He could understand the frustrations of his girlfriends, his running off and canceling things at the drop of the hat, but he had reasons, good reasons. For as much of a genius as Sherlock may have been, he had an uncanny ability for getting himself into life threatening situations that even his massive intellect could not get him out of. John was just protecting his best friend. There was no one else that could do it.

At first, John had thought Irene was simply a puzzle that Sherlock kept close to try to solve, but as time passed and John watched the game they played, he realized that there was true emotion there, emotion that Sherlock tried to hide. John may not have been a genius or able to deduce things the way Sherlock could, but he could see the obvious, the little tells which were impossible to miss as much as he wished he could.

But as Sherlock had sunk into depression after Irene disappeared, the silence became unbearable, forcing John to reevaluate some things: where he stood with Sherlock, what Sherlock was to him, if he was happy. The answers didn't help him: he didn't know; had no idea; and definitely not. For all John could read in Sherlock, he didn't even know himself nearly as well as he though he had, and that scared him, made him think, look at the entirety of their relationship, the year they'd lived together.

From the beginning people had assumed them to be partners in the sexual sense, and after a time John had stopped denying it, not because he believed it, but because he knew when to pick his battles and this was one that he seemed unable to win. And that was where it all apparently went wrong because John hadn't thought about it, not really, had just let it go as with so many things connected to Sherlock.

For all John thought he knew himself, he realized he was incredibly good at hiding from the truth. Jealousy. John had been jealous of Irene. With that awareness, everything came tumbling down. It wasn't normal to trust someone so quickly, to kill for someone he barely knew, yet he had and he didn't regret it. John had been astounded by what Sherlock could do, how much he could know from the tiny details that no one else paid attention to.

John lied, telling Sherlock Mycroft's fabricated story. He hadn't meant to, hadn't been going to, but the words came out. There was no way Sherlock missed it, and as Sherlock looked right through him, John floundered.

Until Sherlock asked for Irene's phone.

John hadn't realized the true depth of Sherlock's feelings for her until that moment, and he flashed back to that first night in the cab.

If she'd left him, he would have kept it. People do. Sentiment.

John was in love with his best friend. The sudden knowledge was like a punch to the gut, and as he handed it over, watching as Sherlock's fingers curled around it, his heart bled. John turned and ran, hoping, praying that Sherlock hadn't read it on his face if Sherlock didn't know already. John was no coward, but this was something he wasn't prepared to face. The war was already lost, and he was left to pick up the pieces before he even knew there had been a battle.