An adaptation of Sherlock Holmes set in a world in which the fictional character/literary juggernaut Sherlock Holmes, and all the subsequent adaptations thereof, still exist.
Sherlock Holmes (pronounced Holl-mess, as he is constantly reminding people) just had the misfortune of having parents who really liked the books, and his attitude towards his fictional counterpart is pretty much the same as that of Sir Arthur Conan Doyle.
Sherlock runs a Youtube Theory channel called Mysteries Unwrapped with Sherlock Holmes. He has received no less than seven cease and desist letters from the Conan Doyle estate, all of which he has so faded managed to rebuff by pointing out that that's literally his name.
(No he won't change his name. He's Sherlock Holmes the real live human person. Let Sherlock Holmes the non existent fictional character change his name.)
John is Sherlock's flatmate. Sherlock almost refused to live with him once he realised that it would mean staying with a medical student named John, and only gave in once John pointed out that: a) he's a biomedical student, which is completely different from an md, and b) his surname isn't Watson.
It's now been three years, which is long enough for them to have developed a genuine friendship, and for John to have a) started working towards his PhD in biotechnology, and b) for him to start dating somebody with the surname Watson.
Sherlock can feel the narrative closing in.
His Youtube channel is meant to be focused on lost media, fan theories and stuff like that, but he keeps accidentally stumbling upon and then solving genuine crimes.
His brother Mycroft may or may not have chosen that name after he transitions specifically to annoy him.
He doesn't even live in London, but somehow the only flat they could afford was on a street named fucking Baker Street.
Sherlock Holmes and the Unescapable Power of the Narrative.