Sherlock is an aspiring artist with literally nothing except some dried old paints to his name, living in the same ratty old apartment building with his best friend, Molly Hooper. Eventually, the unoccupied apartment across the hall gets a new resident, a cheerful and slightly annoying John Watson. Johnlock Fluff
Assistant Professor Sherlock teaches seventh year John in potions Johnlock fluff :)
Mycroft Holmes and Harry Watson team up to send John and Sherlock on a case to distract a Sherlock who's been pining after John. And Harry, at least, is determined to get the boys together. Two sets of Holmes & Watson shenanigans ensue. (Johnlock, post-S2 AU)