Love Is A Much More Capricious Communicator

For a prompt: When Sherlock first lays eyes on John, it's love at first sight. Unfortunately, Sherlock is sort of a two-year-old about emotions, and gets clumsy, tongue-tied and stupid every time he tries to speak to John. As everyone goes on about how brilliant Sherlock is, John is left wondering if they're talking about the same Sherlock Holmes. Because the Sherlock he knows is barely capable of stringing together a coherent sentence.