Sherlock somehow discovers the wealth of fan art (i.e. porn) on Tumblr about him and John. He's never been in a physical relationship before, but he's starting to realize he'd quite like to try sex with John. Luckily, Tumblr seems to have no end of illustrated guides for wooing John (or so he believes).

John, of course, is totally broadsided when Sherlock basically greets him one day with "I bought you milk, jam, and new red pants, and made you tea. I believe that's the appropriate courting ritual. Can we have sex now? I know what you like because I've done my research on the internet."